JP3369018B2 - Optical cross connect and wavelength division type optical transmission system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cross connect and a wavelength division multiplexing type optical transmission system using the same.
In particular, it relates to an optical cross-connect configuration method for a wavelength division multiplexing optical transmission system having a self-healing function.

[0002]

2. Description of the Related Art With the increase in speed and capacity of information, a transmission system using optical technology is expected as a broadband transmission system in the future. Conventionally, the optical transmission line and the transmission system have been downsized and made economical by increasing the time division multiplexing, but the speed has come to a limit.

On the other hand, with the increase in transmission capacity, optical transmission line failure has a great influence. Therefore, it is necessary to circulate the information disconnected by the failure to a normal optical transmission line to recover the failure (self-healing). One of these solutions is wavelength division multiplexing (WDM: Wavelength-Divisio).
n Multiplexing) technology is a promising configuration.

Here, when the optical technology is used, it does not mean that all of the signals are converted into optical signals in the transmission system, but means that they are combined with electrical processing. A general example of the overall configuration is shown in FIG. In the configuration of such a transmission system, the optical cross connect 21
0, an electrical cross connect 211, a branching part 212 and an inserting part 213.

The optical cross connect 210 performs switching in units of wavelength. Specifically, it converts an optical signal of an arbitrary input highway and an arbitrary wavelength into an arbitrary output highway and an arbitrary wavelength. The electric cross connect 211 processes a signal time-division multiplexed within the wavelength.

Further, the branching unit 212 inputs the working wavelengths λS1 to λSn and the spare wavelengths λP1 to λPn from the input highway, selects the optical signal λSi or λPi of a predetermined wavelength, and inputs it to the electrical cross connect 211. To do. The insertion part 213 is
The optical signal λ 0 from the electric cross connect 211 is converted into a predetermined wavelength and sent to the output highway.

On the other hand, there is a system using a spare wavelength as self-healing in which a wavelength division multiplexing technique is introduced. The operation principle is shown in FIG. Optical cross connect (OXC
-AOXC: Optical Cross-Connect) 220 to Optical Cross-Connect (OXC-C) 222, Optical Cross-Connect (O
XC-E) 224, while transmitting the optical signals a1 to an of the working wavelengths λS1 to λSn, the optical cross connect (OXC-A) 220 and the optical cross connect (OXC-A) are transmitted.
C) Consider a case where a failure occurs in the optical transmission line between 222.

In this case, the optical cross connect (OXC-
A) 220 diverts an optical signal to the optical cross connect (OXC-E) 222 via the optical cross connect (OXC-B) 221 using the spare wavelengths λP1 to λPn.

37 to 40 show an example of the configuration of a conventional optical cross connect. The configuration example (type A) of FIG. 37 is a wavelength demultiplexer (WDMUX: Wavelength Demultip
lexer) 230, 2 nk x 2 nk optical space switch 23
1. Wavelength multiplexer for each output highway (WMUX: Wavelength M
ultiplexer) 232.

The wavelength demultiplexer 230 has 2n fixed wavelength filters FFIL (Fixed Wavelength Filter), and the wavelength multiplexer 232 has 2n fixed wavelength converters FCNV (Fixed).
Wavelength Converter). The wavelength demultiplexer 230 demultiplexes the wavelength, the optical space switch 231 routes the signal to a desired outgoing link, and the wavelength multiplexer 232 converts it to a predetermined wavelength.

The configuration example (type B-1) of FIG. 38 is a wavelength switch (λSwitch) 240, k × for each incoming highway.
It comprises an optical coupler 241 of k and a wavelength switch 242 for each output highway. The front wavelength switch 240 is composed of 2n fixed wavelength filters FFIL and 2n fixed wavelength converters FCNV, and the rear wavelength switch 242 is 2n.
Tunable Wavelength F
ilter) and 2n fixed wavelength converters FCNV.

2nk optical signals (optical signals of wavelengths λs1 to λsn × k and λp1 to λpn × k) are output by the wavelength switch 240 in the preceding stage.
Are converted into different wavelengths, combined by a coupler 241, and distributed to all outgoing links. Then, a desired wavelength is selected by the wavelength switch 242 in the subsequent stage and converted into a predetermined wavelength.

The configuration example (type B-2) of FIG. 39 comprises a wavelength switch 250 for each incoming highway, an optical coupler 251 of k × k, and a wavelength switch 252 for each outgoing highway. The wavelength switch 250 in the preceding stage includes 2n fixed wavelength filters FFIL and 2n variable wavelength converters TCNV (Tu
nable Wavelength Converter), and the second stage wavelength switch 252 includes 2n fixed wavelength filters FFIL and 2
It consists of n fixed wavelength converters FCNV.

The wavelength switch 250 at the preceding stage converts the wavelengths of the 2nk optical signals according to the destination outgoing link, merges them by the coupler 251, and distributes them to all outgoing links. Then, the wavelength switch 252 in the subsequent stage selects a predetermined wavelength and converts it into a predetermined wavelength.

The conventional configuration example (type C) of the cross-connect shown in FIG. 40 is a wavelength-division multiplexed signal for working and protection of each incoming highway (working: λW1 to λWn, protection: λR1 to λRn).
2 fixed wavelength filters (F
FIL) 260, three-stage optical switch circuits 261-263
(First stage: k 2n × 4n optical switches 261, second stage: 4n k × k switches 262, third stage: k 4
n × 2n optical switch 263) and k number of 4n in the third stage
Wavelength signals for working and protection of each output highway from the × 2n optical switch 263 (working: λW1 to λWn, protection: λR1
~ ΛRn) 2nk wavelength converters (FCNV)
It consists of H.264. As a result, the optical switch routes each wavelength signal to a desired outgoing link, and the wavelength converter converts it to a predetermined wavelength.

[0016]

In the configuration of the conventional optical cross-connect as described above, in the configuration of type A shown in FIG. 37, the number of wavelengths used is 2n, but 4n ² k ^{2 is used.}
Since there is a need for individual optical switches, there is a problem that the amount of hardware becomes large.

On the other hand, in the type B configuration shown in FIGS. 38 and 39, 4 nk wavelength filters and 4 nk wavelength converters are sufficient, but the number of wavelengths used is as large as 2 nk, and the demand for wavelength devices is increased. There is a problem that the characteristics become strict.

Furthermore, in the type C configuration example shown in FIG.
Intermediate stage (second stage) for complete non-block configuration
It is necessary to set the number of optical switches of 4n to 4n, and there is a problem that the amount of hardware becomes large as in the other examples described above. That is, the reason for setting 4n can be calculated from the definition of Clos. The number of optical signals entering the first-stage optical switch is 2n, and the number of optical signals exiting the third-stage optical switch is 2n, and at the same time, there are path connections that are in these two states. Is required to add 4n.

Therefore, it is an object of the present invention to provide an optical cross connect and a wavelength division multiplexing type optical transmission system using the same, which solves the problems in the conventional configuration.

[0020]

The basic structure of an optical cross-connect according to the present invention, which solves the problems of the above-mentioned conventional example, comprises a routing part and a bypass part, and the routing part is an active part from an incoming highway. When the wavelength of the optical signal of the wavelength is converted to the desired wavelength and is output to the desired output highway, and the failure of the optical transmission line occurs, the wavelength of the optical signal flowing through this transmission line is spared. The wavelength is converted to a normal route, the wavelength is converted to a normal route, and the wavelength of the optical signal that has entered with the backup wavelength is returned to the working wavelength and output to a predetermined route.

Further, the bypass section is configured to output the optical signal input with the spare wavelength to the predetermined route with the same wavelength.

As a specific feature, the routing unit is
A wavelength switch composed of n variable wavelength filters and n variable wavelength converters is provided on each cross point of the matrix. As a result, the variable wavelength switch of each wavelength switch can select a desired wavelength from the wavelength-multiplexed optical signals of the working and standby wavelengths and convert it to the desired wavelength.

Further, as another feature, the routing section is formed by cascading two switch modules each having a switch element consisting of one wavelength filter and one wavelength converter on each cross point of the matrix. It

In this case, the switch element of the first-stage switch module selects a desired wavelength from the wavelength-multiplexed optical signals of the working and standby wavelengths and converts them into different wavelengths so that the wavelengths do not overlap on the link between the modules. To do.

Then, each switch module in the second stage selects an optical signal to a predetermined output highway and converts it into a predetermined wavelength.

As another feature, the bypass section is configured to have one multi-wavelength selection filter on each cross point of the matrix.

Further, as a feature, the bypass section is configured to have one multi-wavelength selection filter for each input highway and an optical space switch to which the output of the multi-wavelength selection filter is connected.

In the above-mentioned bypass section, each multi-wavelength selection filter normally blocks the optical signals of both the working and spare wavelengths, and the spare wavelength is passed only when the spare wavelength optical signal is bypassed. Tuned.

A wavelength division multiplexing optical transmission system according to the present invention is an optical cross connect having the above characteristics.
This optical cross-connect is connected to the front stage, is provided with a plurality of variable wavelength filters, is connected to a branching unit, is connected to the rear stage, is provided with an insertion unit having a plurality of variable wavelength converters, and optical / electrical conversion and electrical / optical conversion functions. With each electrical cross-connect with.

The branching unit sends the wavelength-multiplexed optical signal from each input highway to the electrical cross-connect through the plurality of variable wavelength filters, and the inserting unit outputs the optical signal from the electrical cross-connect. The variable wavelength converters are configured to be output to the output highway.

Further, as a feature, in the above, an optical signal disconnection detection unit including a variable wavelength filter and a monitor is provided on the input / output side of each optical transmission line to detect a fault in the optical transmission line and a fault in the transmission system device, and to perform normal operation. Configured to control detours to the route.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or similar items
Description will be given with the same reference numerals and symbols.

FIG. 1 shows a principle block diagram of an optical cross-connect 210 according to the present invention used in a system of the present invention. This optical cross connect is composed of two parts, a routing part 1 and a bypass part 2.

The function of the routing unit 1 is as follows.
The wavelength of the optical signal input from the input highway at the working wavelengths λS1 to λSn is switched to the desired wavelength so as to be output to the desired output highway through the coupler 4.

Here, when a failure occurs in the optical transmission line, the optical cross connect 210 converts the wavelength of the optical signal flowing through it into the spare wavelengths λP1 to λPn, and detours to the normal route. . Further, it has a function of returning the wavelength of the optical signal input with the spare wavelengths λP1 to λPn to the working wavelengths λS1 to λSn and switching to a predetermined route.

On the other hand, the function of the bypass section 2 is to switch the optical signal, which is branched by the coupler 3 and input with the preliminary wavelengths λP1 to λPn, to the predetermined route with the wavelength as it is and to output it through the coupler 4.

2 to 5 show examples of the configuration of the routing unit 1 as an embodiment of the present invention. Type A in FIG. 2 is k × k
The wavelength switch 21 is arranged at each of the cross points 201 to 2kk of the matrix. Each wavelength switch 21
Consists of n variable wavelength filters TFIL and n variable wavelength converters TCNV.

In FIG. 2, a variable wavelength filter TFIL of each wavelength switch 21 selects a desired wavelength from the wavelength-multiplexed optical signals of the working and standby wavelengths, and the variable wavelength converter T
Convert to desired wavelength with CNV.

FIGS. 3 and 4 show types B-1 and B, respectively.
2 is a configuration example of the routing unit 1 classified into −2, and one wavelength filter TF is provided on each cross point of Matrisk.
Two switch modules 30 and 31 in which a switch element SE (Switch Element) including an IL and one wavelength converter FCNV is arranged are cascaded.

In the type B-1 shown in FIG. 3, the wavelength filter TFIL of the switch element SE constituting the first-stage switch module 30 is variable, the wavelength converter FCNV is fixed, and the second-stage switch module 31 is constituted. The switch element SE to be operated is variable in both the wavelength filter TFIL and the wavelength converter TCNV.

In FIG. 3, the variable wavelength filter TFIL of each switch element SE of the first-stage switch module 30 selects a desired wavelength from the wavelength-multiplexed optical signals of the working and spare wavelengths, and the fixed wavelength converter FCNV. Convert to different wavelengths so that wavelengths do not overlap on links between modules.

The variable wavelength filter TFIL of each switch element SE of the second-stage switch module 31.
Selects an optical signal to a predetermined output highway, and the variable wavelength converter TCNV converts the optical signal into a predetermined wavelength.

In the type B-2 shown in FIG. 4, the switch element SE constituting the first-stage switch module 30 is variable in both the wavelength filter TFIL and the wavelength converter TCNV, and the second-stage switch module 31 is Wavelength filter FFIL of switch element SE
Is fixed, and the wavelength converter TCNV is variable.

In FIG. 4, the variable wavelength filter TFIL of each switch element SE of the first-stage switch module 30 selects a desired wavelength from the wavelength-multiplexed optical signals of the working and standby wavelengths, and the variable wavelength converter TCNV. Convert to the desired wavelength.

Then, the fixed wavelength filter FFIL of each switch element SE of the second-stage switch module 31.
Selects an optical signal to a predetermined output highway, and the variable wavelength converter TCNV converts the optical signal into a predetermined wavelength.

FIG. 5 shows a space division type equivalent circuit of the type B routing unit 1 including the types B-1 and B-2. That is, it has a first stage, a second stage and a third stage matrix switch, and the first stage and the third stage are represented by 2n × 2n, and the second stage is represented by a k × k matrix switch.

FIGS. 6 and 7 show an example of the configuration of the bypass section 2 as an embodiment. The configuration of type A shown in FIG. 6 is
One multi-wavelength selective filter MWFIL (Multi-Wavele) is provided on each cross point of the k × k matrix.
ngth Filter).

In FIG. 6, a predetermined multi-wavelength selection filter MWFIL collectively extracts the wavelength-multiplexed optical signals of the preliminary wavelengths .lambda.P1 to .lambda.Pn and sends them to a predetermined link. Here, each multi-wavelength selection filter MWFIL normally blocks both the optical signal of the working wavelength and the spare wavelength, and the transmission wavelength of the filter is tuned to the spare wavelength only when the optical signal of the spare wavelength is bypassed.

The type B shown in FIG. 7 comprises a multi-wavelength selection filter MWFIL for each input highway and a k × k optical space switch 7. In this type, a predetermined multi-wavelength selection filter MWFIL collectively extracts the wavelength-multiplexed optical signals of the preliminary wavelengths .lambda.P1 to .lambda.Pn, and the optical space switch 7 sends them to the predetermined outgoing links 1 to k.

Here, each multi-wavelength selection filter MWFIL
Normally blocks both the optical signal of the working wavelength and the spare wavelength, and tunes the transmission wavelength of the filter to the spare wavelength only when bypassing the optical signal of the spare wavelength.

Next, an operation example of the routing unit 1 and the bypass unit 2 having the above-described structure according to the present invention will be shown together with an example of self-healing.

FIG. 8 shows an example of self-healing operation.
Optical Cross Connect (OXC-A OXC: Optical Cross-Con
nect) 220 to optical cross connect (OXC-C) 22
2. Optical cross-connect (OXC-A) 220 and optical cross-connect (OXC-A) 220 are transmitting optical signals a1 to a4 at working wavelengths λs1-λs4 using the path of optical cross-connect (OXC-E) 224. -C) Assume that a failure occurs in the optical transmission line between 222.

In this case, the optical cross connect (OXC-
A) 220 diverts an optical signal to the optical cross connect (OXC-C) 222 via the optical cross connect (OXC-B) 221 using the spare wavelength (λp1−λp4).
Therefore, the optical cross connect (OXC-B) 221 receives the backup wavelength λp1 from the optical cross connect (OXC-A) 220.
The optical signals a1 to a4 of-[lambda] p4 are bypassed and sent to the optical cross connect (OXC-C) 222.

Further, optical cross connect (OXC-C) 2
Reference numeral 22 denotes the backup wavelengths λp1 to λp4 of the optical signals a1 to a4 from the optical cross connect (OXC-B) 221 and the working wavelength λ.
Optical cross connect (OXC-E) 22 by returning to s1-λs4
Send to 4.

9 to 11 show the optical cross connect (O
XC-A) 220, optical cross connect (OXC-B) 2
21 is an operation example of the type A routing unit 1 (see FIG. 2) in the optical connection unit 21 and the optical cross connect (OXC-C) 222.

Similarly, in each of FIGS. 12 to 14, the optical cross connect (OXC-A) 220, the optical cross connect (OXC-B) 221, and the optical cross connect (OXC-
C) Type B routing unit 1 in 222 (FIG. 3,
(See FIG. 4).

15 and 16 are operation examples of the type A bypass section 2 (see FIG. 6) and the type B bypass section 2 (see FIG. 7) in the optical cross connect (OXC-B) 221. .

The wavelength switch 21, the switch element SE, and the multi-wavelength selection filter MWFIL, which are shaded in these figures, indicate that they are performing predetermined operations.

First, in FIG. 9, in the normal state, the input highway 2 of the optical cross connect (OXC-A) 220 is shown.
The optical signals a1 to a4 of wavelengths λs1 to λs4 are input to (I2) and output through the wavelength switch 21-1 to the highway 1 (O
1) is output as optical signals a1 to a4 having wavelengths λs1 to λs4.

At this time, when the output highway 1 (O1) fails, the wavelength switch 21-2 is activated instead of the wavelength switch 21-1, and the wavelength switch 21-2 is converted to wavelengths λp1 to λp4 through the optical signal a1. ~ A4 is output to the output highway 4 (O4).

The optical signals b1 to b4 of wavelengths λs1 to λs4 input to the input highway 3 (I3) are transmitted by the wavelength switch 2
It is similarly output to the output highway 4 (O4) through 1-3.

Here, referring to FIG. 8, the output highway 4 (O4) of the optical cross connect (OXC-A) 220.
Is connected to the input highway 2 (I2) of the optical cross connect (OXC-B) 221 via an optical transmission line. Therefore, in the optical cross connect (OXC-B) 221, as shown in FIG. 10, the optical signals b1 to b4 of the wavelengths λs1 to λs4 input to the input highway 2 (I2) pass through the wavelength switch 21-4. , Output highway 3 (O3).

Optical cross connect (OXC-B) 2
21 wavelengths λs1 to the input highway 4 (I4)
The optical signals c1 to c4 of .lambda.s4 pass through the wavelength switch 21-5 and are output to the output highway 1 (O1).

On the other hand, the optical cross connect (OXC-A) 2
20 and the optical cross connect (OXC-C) 222 are converted to wavelengths .lambda.p1 to .lambda.p4 for detouring due to a line failure, and the optical signals a1 to a4 are converted into the optical cross connect (OXC-C).
B) When input to 221, it is output to the output highway 1 (O1) through the bypass unit 2.

That is, when the bypass unit 2 has the type A configuration shown in FIG. 15, as shown in the drawing, the multi-wavelength selection filter connected between the input highway 2 (I2) and the output highway 1 (O1). Wavelengths λp1 to λp4 pass through the MWFIL
Optical signals a1 to a4 are output to the output highway 1 (O1).

If the bypass unit 2 has the type B configuration shown in FIG. 16 (see FIG. 7), the incoming highway 2
The multi-wavelength selective filter MWFIL connected to (I2) has the selectivity of the wavelengths .lambda.p1 to .lambda.p4, and therefore the optical signals a1 to a4 of the wavelengths .lambda.p1 to .lambda.p4 are input to the optical space switch 7.

Further, in the optical space switch 7, the wavelength λ
Output optical signals a1 to a4 of p1 to λp4 Highway 1 (O1)
The connection is controlled to output to.

Next, returning to FIG. 11, the explanation will be made with reference to FIG.
FIG. 6 is a diagram illustrating an operation example of a type A routing unit 1 in an optical cross connect (OXC-C) 222.
Optical signals c1 to c4 of wavelengths .lambda.s1 to .lambda.s4 and optical signals a1 to a4 of wavelengths .lambda.p1 to .lambda.p4 are input to the input highway 4 (I4) of the optical cross connect (OXC-C) 222.

The optical signals c1 to c4 of the wavelengths λs1 to λs4 pass through the wavelength switch 21-6, are output to the output highway 2 (O2), and are directed to the optical cross connect (OXC-D) 223.

On the other hand, optical signals a1 to a4 of wavelengths λp1 to λp4
Passes through the wavelength switch 21-7, is converted into wavelengths λs1 to λs4, and is output to the output highway 1 (O1). As a result, the wavelength λs1 output to the output highway 1 (O1)
The optical signals a1 to a4 of .lambda.s4 are the optical cross connect (OX
C-E) 224 can be reached.

Next, the operation of the routing unit in the case of type B will be described with reference to FIGS. In FIG. 12, in the normal state, the optical cross connect (OXC-A) 2
The optical signals a1 to a4 of wavelengths .lambda.s1 to .lambda.s4 are input to the incoming highway 2 (I2) of 20 and switch elements SE1 to S4 are input.
Exit Highway 1 through E4 and SE11-SE14
The optical signals a1 to a4 having wavelengths .lambda.s1 to .lambda.s4 are output to (O1).

At this time, if a failure occurs in the output highway 1 (O1), the switch elements SE01 to SE04 are activated instead of the switch elements SE11 to SE14, through which the optical signals a1 to a4 of wavelengths λp1 to λp4 are transmitted. It is output to the output highway 4 (O4).

Referring to FIG. 8, the optical cross connect (O
The outgoing highway 4 (O4) of the XC-A) 220 enters the incoming highway 2 (I4) to the optical cross connect (OXC-B) 221.
2) is connected. Furthermore, optical cross connect (OX
In CB) 221, as shown in FIG. 13, the optical signals b1 to b4 of wavelengths λs1 to λs4 input to the input highway 2 (I2) pass through the switch elements SE21 to 24 and SE31 to 34 and are output. It is output to highway 3 (O3).

The optical cross connect (OXC-B) 2
21 wavelengths λs1 to the input highway 4 (I4)
The optical signals c1 to c4 of .lambda.s4 are sent to the switch element SE4.
1-44 and SE 51-54, exit highway 1
It is output to (O1).

On the other hand, the optical cross connect (OXC-A) 2
20 and the optical cross connect (OXC-C) 222 are converted to wavelengths .lambda.p1 to .lambda.p4 for detouring due to a line failure, and the optical signals a1 to a4 are converted into the optical cross connect (OXC-C).
B) When input to 221, it is output to the output highway 1 (O1) through the bypass unit 2.

That is, when the bypass unit 2 has the type A configuration shown in FIG. 15, as shown in the drawing, the multi-wavelength selection filter connected between the input highway 2 (I2) and the output highway 1 (O1). Wavelengths λp1 to λp4 pass through the MWFIL
Optical signals a1 to a4 are output to the output highway 1 (O1).

When the bypass section 2 has the type B configuration shown in FIG. 16 (see FIG. 7), the input highway 2
The multi-wavelength selective filter MWFIL connected to (I2) has the selectivity of the wavelengths .lambda.p1 to .lambda.p4, and therefore the optical signals a1 to a4 of the wavelengths .lambda.p1 to .lambda.p4 are input to the optical space switch 7.

Further, in the optical space switch 7, the wavelength λ
Output optical signals a1 to a4 of p1 to λp4 Highway 1 (O1)
The connection is controlled to output to.

Next, returning to FIG. 14 and explaining, FIG.
3 is an operation example of the type B routing unit 1 in the optical cross connect (OXC-C) 222. In the input highway 4 (I4) of the optical cross connect (OXC-C) 222, optical signals c1 to c4 having wavelengths λs1 to λs4 and wavelengths λp1 to λ4.
The optical signals a1 to a4 of p4 are input.

The optical signals c1 to c4 of the wavelengths λs1 to λs4 pass through the switch elements SE61 to 64 and SE71 to 74, are output to the output highway 2 (O2), and are directed to the optical cross connect (OXC-D) 223.

On the other hand, the optical signals a1 to a4 of wavelengths λp1 to λp4
Are switch elements SE81-84 and SE91-
The signals are converted into wavelengths λs1 to λs4 by 94 and output to the output highway 1 (O1). As a result, the optical signals a1 to a4 output to the output highway 1 (O1) can reach the optical cross connect (OXC-E) 224.

FIG. 17 shows a configuration example of the wavelength converter. In FIG. 17, the structure (a) is a wavelength conversion element based on a semiconductor laser diode (LD). The wavelength can be tuned by controlling the injection current of the semiconductor LD, and the wavelength conversion can be performed as light-light.

Further, the configuration of FIG. 17B has an electric / electrical converter (O / E) and an electric / electrical converter directly modulated by the variable wavelength LD.
It is composed of an optical converter (E / O), and the wavelength is tuned by controlling the injection current to the variable wavelength LD.

Further, the configuration of FIG. 17C is a wavelength converter by an external modulation method using O / E, a variable wavelength LD and a LiNbO ₃ (LN) optical modulator. The wavelength is tuned by controlling the injection current to the variable wavelength LD.

On the other hand, as the wavelength filter FIL, there are a dielectric multilayer filter, a grating type filter, a Fabry-Perot filter, an acousto-optic filter, a semiconductor filter and the like.

Further, the multi-wavelength selection filter MWFIL can be constituted by an acousto-optic filter or a filter in which all the optical signals of the spare wavelength are within the half-value width with the working wavelength band and the spare wavelength band being slightly apart.

In FIGS. 18 and 19, branching section 212 is shown.
(See FIG. 21) and an example of the configuration of the insertion portion 213 (see FIG. 1) are shown. 18, in the branching unit 212, the wavelength-multiplexed optical signal from each input highway is sent to the electrical cross connect 211 (see FIG. 21) through a plurality of variable wavelength filters TFIL.

Further, in the inserting section 213, the optical signal (wavelength λ ₀ ) from the electric cross connect 211 is sent to the output highway through the plurality of variable wavelength converters TCNV.

FIG. 20 shows an example of the configuration of the optical signal break detecting unit. The function of this detection unit is to detect a failure in the optical transmission path and to detect a failure in the transmission system device.
Therefore, the variable wavelength filter TFIL and the monitors 201 to 201 are provided on the input side of the optical cross connect connected to each optical transmission line.
20 k, and a variable wavelength filter TFIL and monitors 301 to 30 k are provided on the output side.

Monitors 201-20k and 301-30
Based on the detection of the fault due to k, the detour of the optical signal is determined and controlled as described above with reference to FIG.

Further, FIGS. 21 and 22 are relationship diagrams showing the number of required optical devices and the number of required wavelengths in comparison with the conventional configuration, respectively.

As can be seen from these relationship diagrams, in the configuration of the present invention, the number of required optical devices can be reduced as compared with the conventional type A configuration (see FIG. 37). The conventional type B configuration (see FIGS. 38 and 39)
Compared with, the number of required optical devices is slightly increased, but the number of required wavelengths can be reduced.

FIG. 23 shows an example (type C-1) in which the routing unit 1 of FIG. 1 is constructed according to the present invention corresponding to the conventional example of FIG. As compared with the conventional configuration of FIG. 40, the number of the optical switches 262 in the middle stage, that is, the second stage of the three-stage circuit of the optical switch is 3n.

This is the bypass unit 2 which will be described later in the operation example.
It is due to the provision of. By providing the bypass unit 2, the number of optical signals entering the one optical switch 261 in the first stage and the one optical switch 263 in the third stage are generated in the conventional configuration of FIG. 40. This is because there is no longer a situation where the number of optical signals becomes 2n at the same time. That is, when 2n optical signals are input to the first-stage optical switch 261, the number of optical signals output to the third-stage optical switch 263 is n. The reverse is also possible.

FIG. 24 is another example (type C-2) of the routing unit 1 of FIG. 1 according to the present invention corresponding to the conventional example of FIG.

In this configuration example, the optical signal of a predetermined wavelength is collected from each input highway and the first stage switch 2
The optical signal is output to a separate output highway after being input to the output terminal 61 and converting the output optical signal of the third-stage optical switch 263 into a predetermined wavelength. In this configuration, the number of input / output optical signals to / from each of the first-stage and third-stage optical switches is k regardless of the presence or absence of a transmission path failure. Therefore, the number of intermediate-stage optical switches 262 is 2k.

23 and 24, the working wavelengths are represented by λW1 to λWn and the backup wavelengths are represented by λR1 to λRn in correspondence with FIG. 40 of the conventional example. Working wavelength λ S1 in the embodiment described in
λSn and the preliminary wavelengths λP1 to λPn.

Therefore, the operation of self-routing will be described below with reference to FIG. 25 using the routing unit 1 according to the present invention shown in FIGS. 23 and 24. Similarly, the working wavelength according to the previous embodiment will be described. λS1 to λSn are λW1 to λWn,
Further, it is assumed that the preliminary wavelengths λP1 to λPn are replaced with λR1 to λRn.

Further, in the following description of the operation of self-routing, the bypass unit of the type A shown in FIG. 6 is used as the structure of the bypass unit corresponding to the structure (type C-1) of the routing unit of FIG. The type B bypass unit shown in FIG. 7 is used in correspondence with the configuration of the routing unit (type C-2) shown in FIG.

25, the routing unit 1 and the bypass unit 2 according to the present invention corresponding to the conventional example of FIG.
The operation example will be described by taking the same failure recovery as in the case of FIG. 8 as an example.

That is, in FIG. 25, from the optical cross connect (OXC-A) 220 to the optical cross connect (OXC-A).
C) 222 and (OXC-E) 224 are used to transmit the optical signals (a1, a2) at the working wavelengths (λw1, λw2), the optical cross-connects (OXC-A) 220 and (OXC-A) 220 and (OXC-A) 220 are transmitted. -C) Assume that the optical transmission line between 222 has failed.

In this case, the optical cross connect (OXC-
A) 220 diverts the optical signal to the optical cross connect (OXC-C) 222 via the optical cross connect (OXC-B) 221 using the spare wavelengths (λR1, λR2).

Therefore, the optical cross connect (OXC-B) 2
21 bypasses the optical signal of the backup wavelength from the optical cross connect (OXC-A) 220 and sends it to the optical cross connect (OXC-C) 222. Furthermore, the optical cross connect (OXC-C) 222 is an optical cross connect (OXC-C).
CB) wavelengths λR1 to λ of the optical signal of the backup wavelength from 221
Rn is returned to the current wavelengths λW1 to λWn and sent to the optical cross connect (OXC-E) 224.

The route as described above is provided by the optical cross connect (OXC-A) 22 shown in FIGS.
0, (OXC-B) 221, (OXC-C) 222, an operation example of the routing unit 1 (type C-1), and the bypass unit 2 provided in the optical cross connect (OXC-B) 221 shown in FIG. The operation example of (type A) is explained as follows.

That is, the optical cross connect (OXC-A) 2
The signals (a1, a2) of the working wavelengths λW1 and λW2 input to the second input terminal of 20 through the distributor 265 are filtered by the filter 2
60 and the corresponding second optical switch of the first-stage optical switch 261 to be input to the first and second optical switches of the second-stage optical switch 262. Further, it passes through the third-stage optical switch 263, and the corresponding wavelength converter 264 4
The second wavelength converter converts the auxiliary wavelengths λR1 and λR2 and outputs the auxiliary wavelengths via the coupler 266.

On the other hand, the optical cross connect (OXC-A) 2
The signals (b1, b2) of the working wavelengths λW1 and λW2 input to the third input terminal of 20 are input to the fifth and sixth optical switches of the second-stage optical switch 262. Further, the light passes through the third-stage optical switch 263, and is output by the fourth wavelength converter of the corresponding wavelength converter 264 via the coupler 266 while keeping the working wavelengths λW1 and λW2.

Optical cross connect (OXC-B) 2
21. Similarly, the signals (b1, b2) of the working wavelengths λW1 and λW2 input to the second optical switch of the first-stage optical switch 261 are the third-stage optical switch while the working wavelengths λW1 and λW2 remain unchanged. It is output via the third optical switch 263.

The signals (c1, c2) of the working wavelengths λW1 and λW2 input to the fourth optical switch of the first-stage optical switch 261 are the working wavelengths λW1 and λW2 of the first-stage optical switch 263. It is output via the first optical switch.

On the other hand, the signals (a1, a2) converted into the spare wavelengths λR1 and λR2 and input to the optical cross connect (OXC-B) 221 are blocked by the first-stage optical switch 261 of the routing unit 1 and bypassed. Input to part 2. FIG. 29
, The signals of the preliminary wavelengths λR1 and λR2 (a1, a2)
Is input to the input 2 of the bypass unit 2, is selected by the shaded filter of FIG. 29, is output to the terminal 1 with the spare wavelength as it is, and is directed to the optical cross connect 222.

Furthermore, the optical cross connect (O
In the XC-C) 222, the signals (c1) of the working wavelengths λW1 and λW2 from the optical cross connect 221 are input to the fourth input end.
, C2) and the signals (a1, a2) of the preliminary wavelengths that have passed through the bypass section 2 are input.

Of these, the signals of the working wavelengths λW1 and λW2 (c1
, C2) is output from the second output end to the optical cross connect (OXC-D) 223 while keeping the working wavelengths λW1 and λW2. On the other hand, signals of spare wavelengths λR1 and λR2 (a1, a2)
Is converted into working wavelengths λW1 and λW2 and output from the first output end to the optical cross connect (OXC-E) 224.

Therefore, the signals (a1, a2) are transmitted through the optical cross connects (OXC-A) 220 and (OXC-C) 22.
Irrespective of the transmission line failure between the optical cross connect (OXC-A) 220 and the optical cross connect (OXC-A) 220.
E) can be transmitted to 224.

Further, with reference to FIG. 25, operation examples of the failure recovery described above are shown in FIGS. 30 to 32, respectively.
Optical cross connect (OXC-A) 220, (OXC-
B) 221 and (OXC-C) 222 using the routing unit 1 (Type C-2) Further, the bypass unit 2 (Type B) provided in the optical cross connect (OXC-B) 221 shown in FIG. Will be described as follows.

That is, the optical cross connect (OXC-A) 2
The signals (a1, a2) of the working wavelengths λW1 and λW2 input through the distributor 265 at the second input end of 20 are divided into the signals a1 and a2, and pass through the first and second filters 260, respectively. , The first stage optical switch 261
Through the corresponding first and second optical switches of the above, and both are input to the first optical switch of the second stage optical switch 262. Further, the third and third optical switches 263 are separately input to the first and second optical switches, and the corresponding wavelength converter 264 outputs the backup wavelength λ from each of the third optical switches.
It is converted into R1 and λR2 and output through the fourth coupler output terminal of the coupler 266.

On the other hand, the optical cross connect (OXC-A) 2
The signals (b1, b2) of the working wavelengths λW1 and λW2 input to the third input terminal of 20 are input to the second optical switch of the second-stage optical switch 262. Further, it passes through the third-stage optical switch 263, and the fourth wavelength converter of the corresponding wavelength converter 264 uses the coupler 2 while keeping the working wavelengths λW1 and λW2.
It is output via 66.

Optical cross connect (OXC-B) 2
In the same manner, the signals (b1, b2) of the working wavelengths λW1 and λW2, which are input from the second input terminal in the same manner, are input to the filter 2
60, input to the first-stage optical switch 261, passes through the second-stage optical switch 262, and the third output end is passed through the third-stage optical switch 263 and the wavelength converter 264 while keeping the working wavelengths λW1 and λW2. Is output via.

Further, the signals (c1, c2) of the working wavelengths λW1 and λW2 input to the first-stage optical switch 261 through the distributor 265 from the fourth input terminal are similarly the working wavelengths λW1 and λW2. The light is output through the third output switch 263 and the wavelength converter 264 and the first output end.

On the other hand, the signals (a1, a2) converted to the spare wavelengths λR1 and λR2 and input to the optical cross connect (OXC-B) 221 are blocked by the first-stage optical switch 261 of the routing unit 1 and bypassed. Input to part 2. FIG. 33
, The signals of the preliminary wavelengths λR1 and λR2 (a1, a2)
Is input to the input 2 of the bypass unit 2, is selected by the filter shaded in FIG. 33, is output to the terminal 1 via the optical space switch 7 with the spare wavelength as it is, and is directed to the optical cross connect 222. .

Furthermore, the optical cross connect 22 shown in FIG.
2, the working wavelength λW from the optical cross connect 221 input from the fourth input terminal through the distributor 265.
1, the signals of λW2 (c1, c2) and the signals of the preliminary wavelengths (a1, a2) passed through the bypass section 2 are input. Of this,
The signals (c1, c2) of the working wavelengths λW1 and λW2 remain at the working wavelengths λW1 and λW2 from the second output end, and the optical cross connect 2
It is output to 23. On the other hand, the signals (a1, a2) of the spare wavelengths λR1 and λR2 are transmitted by the wavelength converter 264 to the working wavelength λW1,
It is converted to λW2 and output from the first output end to the optical cross connect 224.

Therefore, the signals (a1, a2) are transmitted from the optical cross connect 220 to the optical cross connect 22 regardless of the transmission path failure between the optical cross connects 220 and 222.
4 can be transmitted.

23 to 33, since the wavelength converter 264 has the same structure as that described with reference to FIG. 17, further description will be omitted.

FIG. 34 is a diagram showing the number of required optical devices in the embodiment configuration of the routing section 1 of the present invention shown in FIG. 23, which corresponds to the conventional configuration of FIG. 40, in comparison with the conventional configuration. .

As can be understood from this figure, in the configuration of the embodiment of the routing unit 1 of the present invention shown in FIG. 23 of the present invention, the number of required optical devices can be reduced as compared with the conventional configuration. it can.

[0124]

As described above according to the embodiments,
According to the present invention, by configuring the wavelength division type optical cross-connect with the routing section and the bypass section, it is possible to reduce the number of required optical devices or the required number of wavelengths. Therefore, it greatly contributes to the performance improvement of the transmission system using the optical cross connect.

[Brief description of drawings]

FIG. 1 is a principle configuration block diagram of an optical cross connect according to the present invention.

FIG. 2 is a diagram showing a configuration example (type A) of a routing unit in FIG.

FIG. 3 is a configuration example of a routing unit in FIG. 1 (type B-1).
FIG.

FIG. 4 is a configuration example of a routing unit in FIG. 1 (type B-2).
FIG.

FIG. 5 is a diagram showing a type B space division type equivalent circuit.

FIG. 6 is a diagram illustrating a configuration example (type A) of a bypass unit in FIG.

FIG. 7 is a diagram showing a configuration example (type B) of a bypass unit in FIG.

FIG. 8 is a diagram illustrating an operation example of self-healing using a backup wavelength.

9 is a diagram illustrating an operation example of a type A routing unit 220 in FIG.

10 is a diagram illustrating an operation example of a type A routing unit 221 in FIG.

11 is a diagram illustrating an operation example of a type A routing unit 222 in FIG.

12 is a diagram illustrating an operation example of a type B routing unit 220 in FIG.

13 is a diagram illustrating an operation example of a type B routing unit 221 in FIG.

14 is a diagram illustrating an operation example of a type B routing unit 222 in FIG.

FIG. 15 is a diagram illustrating an operation example of the type A bypass unit in FIG. 8;

16 is a diagram illustrating an operation example of a type-B bypass unit in FIG.

FIG. 17 is a diagram illustrating a configuration example of a wavelength converter.

FIG. 18 is a diagram illustrating a configuration example of a branch unit.

FIG. 19 is a diagram illustrating a configuration example of an insertion unit.

FIG. 20 is a diagram illustrating a configuration example of an optical signal loss detection unit.

FIG. 21 is a relationship diagram for comparing the number of required optical devices.

FIG. 22 is a relationship diagram for comparing required wavelength numbers.

FIG. 23 is a configuration example of a routing part (type C-
It is a figure which shows 1).

FIG. 24 is a configuration example (type C-
It is a figure which shows 2).

FIG. 25 is a diagram showing an operation example of self-healing using a type C routing unit.

FIG. 26 is an example of an operation of a routing part of type C-1 (OX
It is a figure which shows CA.

FIG. 27 is an operation example of a type C-1 routing unit (OX
It is a figure which shows CB).

FIG. 28 is an operation example of a routing part of type C-1 (OX
It is a figure which shows CC.

FIG. 29 is a diagram showing an operation example (OXC-B) of the type A bypass section used in FIG. 25.

FIG. 30 is an example of the operation of the routing part of type C-2 (OX
It is a figure which shows CA.

FIG. 31 is an operation example of a routing part of type C-2 (OX
It is a figure which shows CB).

FIG. 32 is an operation example of a routing part of type C-2 (OX
It is a figure which shows CC.

FIG. 33 is a diagram showing an operation example (OXC-B) of the type B bypass section used in FIG. 25.

FIG. 34 is a diagram comparing the number of required optical devices corresponding to types C-1 and C-2.

FIG. 35 is a diagram showing an overall configuration of an optical transmission system.

FIG. 36 is a diagram illustrating the principle of self-healing using a backup wavelength.

FIG. 37 is a diagram illustrating a configuration example of a conventional optical cross connect.

FIG. 38 shows a configuration example of a conventional optical cross connect (type B
It is a figure explaining -1).

FIG. 39 is a configuration example of a conventional optical cross connect (type B
It is a figure explaining -2).

FIG. 40 is a diagram illustrating a configuration example (type C) of a conventional optical cross connect.

[Explanation of symbols]

210 Optical Cross Connect 211 Electric cross connect 212 fork 213 Insert 1 routing section 2 Bypass section 3, 4 coupler 21 wavelength switch 30, 31 switch module TFIL variable filter FFIL fixed filter TCNV variable wavelength converter SE switch element MWFIL Multi-wavelength selection filter

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-62424 (JP, A) JP-A-58-146149 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04Q 3/52

Claims (8)

(57) [Claims] 1. Input of wavelength-multiplexed optical signals
k input highways and wavelength-multiplexed optical signals
In an optical cross-connect that accommodates a plurality of wavelength-division-multiplexed optical transmission lines via k output highways for outputting , a routing unit and a bypass unit are provided, and the routing unit includes a first matrix and a first matrix.
N tunable wavelength filters on each crosspoint of the lix
And a wavelength switch consisting of n variable wavelength converters,
The wavelength switch, is input from the incoming highways
By converting the working wavelength and the spare wavelength of the optical signal to a desired working wavelength, or when a failure occurs in the wavelength-multiplexed optical transmission line, the wavelength of the optical signal flowing through the wavelength-multiplexed optical transmission line is changed. It is converted to the wavelength of the preliminary and outputs the k-number of output <br/> desired output highway of highway, the bypass portion, connected in parallel with the first matrix
The generated second matrix and each matrix of the second matrix.
With one multi-wavelength selective filter on the loss point,
The multi-wavelength selection filter is used for the optical signal input at the spare wavelength.
The optical cross-connect characterized in that the wavelength is selected by and output to the output highway at the same wavelength. 2. A plurality of wavelength-multiplexed optical transmission lines are accommodated through k input highways for inputting wavelength-multiplexed optical signals and k output highways for outputting wavelength-multiplexed optical signals, respectively. The optical cross-connect includes a routing unit and a bypass unit, and the routing unit has a matrix and a wavelength switch including n variable wavelength filters and n variable wavelength converters on each cross point of the matrix. , The wavelength switch converts the working wavelength and the spare wavelength of the optical signal input from the input highway into a desired working wavelength, or when the wavelength multiplexing optical transmission line has a failure, the wavelength multiplexing converts the wavelength of the optical signal which has been flowing in the optical transmission path to the wavelength of the preliminary and outputs the desired output highway of the k number of output highways, the bypass portion, the Le Quenching of the matrix and the parallel
Connected in rows and connected to each of the k incoming highways
Multi-wavelength selection filter and the multi-wavelength selection filter
The input side is connected to the k input highways, and the output
The optical space switch whose side is connected to the k output highways
The optical signal input at the spare wavelength
Select with a selection filter, through the optical space switch,
Output to the output highway at the selected wavelength
Optical cross-connect, characterized in that configured. 3. Inputting wavelength-multiplexed optical signals respectively
k input highways and wavelength-multiplexed optical signals
Output multiple wavelengths via k output highways
An optical cross-connect for accommodating an optical transmission line is provided with a routing unit and a bypass unit, and the routing unit is provided in each matrix of a matrix that is followed by two stages.
N variable wavelength filters and n variable filters on the loss point
It has a wavelength switch consisting of a wavelength converter and
Of the optical signal input from the input highway.
Convert the working wavelength and spare wavelength to the desired working wavelength, and
In case of failure of the WDM optical transmission line,
The wavelength of the optical signal flowing through the wavelength division multiplexing optical transmission line is
Convert to wavelength and output desired wavelength of the k output highways.
Output to the Iway, and the bypass unit is connected in parallel to the first matrix.
The generated second matrix and each matrix of the second matrix.
With one multi-wavelength selective filter on the loss point,
The multi-wavelength selection filter is used for the optical signal input at the spare wavelength.
And output to the output highway with the same wavelength.
Optical cross-connect, characterized in that configured so that. 4. Inputting wavelength-multiplexed optical signals
k input highways and wavelength-multiplexed optical signals
Output multiple wavelengths via k output highways
An optical cross-connect for accommodating an optical transmission line is provided with a routing unit and a bypass unit, and the routing unit is provided in each matrix of a matrix that is followed by two stages.
N variable wavelength filters and n variable filters on the loss point
It has a wavelength switch comprising a wavelength converter, the wavelength switch
Of the optical signal input from the input highway.
Convert the working wavelength and spare wavelength to the desired working wavelength, and
In case of failure of the WDM optical transmission line,
The wavelength of the optical signal flowing through the wavelength division multiplexing optical transmission line is
Convert to wavelength and output desired wavelength of the k output highways.
Output to the way, and the bypass section is a matrix of the routing section.
Connected in parallel with each of the k incoming highways.
Multi-wavelength selection filter to be continued and the multi-wavelength selection filter
The input side is connected to the k input highways through
An optical space switch whose output side is connected to the k output highways
Switch, and the optical signal input at the spare wavelength is
Select with a wavelength selection filter and pass through the optical space switch.
Output to the output highway at the selected wavelength
Optical cross-connect, characterized in that it is configured. 5. The optical cross connect according to any one of claims 1 to 4, a branch unit connected to a front stage of the optical cross connect and provided with a plurality of variable wavelength filters, and a rear stage unit of the optical cross connect. is has an insertion portion comprising a plurality of variable wavelength converters, each electrical cross-connect with an optical / electrical conversion and electro / optical conversion function, the branch unit, the wavelength-multiplexed from the k pieces of input highways an optical signal sent to the electric <br/> gas cross-connect through said plurality of variable wavelength filter, the insertion portion, the front optical signals from the electrical cross-connect
Serial plurality wavelength division multiplexing optical transmission system, characterized in that it is configured to deliver to said k pieces of output highways through the variable wavelength converter. 6. The optical signal breakage detection unit comprising a variable wavelength filter and a monitor at the input and output sides of the plurality of wavelength division multiplexed optical transmission lines according to claim 5 ,
A wavelength division multiplexing optical transmission system, which is configured to detect a fault in a number of wavelength division multiplexing optical transmission lines and a fault in a transmission system device and control a detour to a normal route. 7. Inputting wavelength-multiplexed optical signals
and k number of incoming highways, each wavelength-multiplexed optical signal
A plurality of wavelength-multiplexed via the k outgoing highway for outputting
In an optical cross-connect that accommodates an optical transmission line, a routing unit and a bypass unit are provided, and the routing unit has 2nk fixed wavelength filters when the number of working wavelengths and the number of spare wavelengths are n and the number of wavelength multiplexing is 2n. K 2n × 3n optical switches provided in the first stage, 3n k × k optical switches provided in the second stage, k 3n × 2n optical switches provided in the third stage, and the three stages The optical switch of the first stage to the third stage is constituted by having 2nk fixed wavelength converters following the optical switch of the eye.
Of the optical signal input from the input highway
Convert the working and backup wavelengths to the desired working wavelength, and
In case of failure of the WDM optical transmission line,
The wavelength of the optical signal flowing through the wavelength division multiplexing optical transmission line is
Convert to wavelength and output desired wavelength of the k output highways.
To the second matrix, and the bypass unit outputs the second matrix and the second matrix.
One multi-wavelength selective fill on each crosspoint of the lix
The optical signal input at the spare wavelength
Select with the selection filter and use the same wavelength as above.
The optical cross connect is characterized in that it is configured to output to an optical output . 8. A plurality of wavelength division multiplexed optical transmission lines are accommodated through k input highways for inputting wavelength multiplexed optical signals and k output highways for outputting wavelength multiplexed optical signals, respectively. The optical cross-connect includes a routing unit and a bypass unit, and the routing unit is provided with 2nk fixed wavelength filters and n provided in the first stage when the number of working and spare wavelengths is n and the number of wavelength multiplexing is 2n. 2k × 2k optical switches, 2k n × n optical switches provided in the second stage, n 2k × 2k optical switches provided in the third stage, and the third optical switch It is configured to have 2 nk fixed wavelength converters connected to each other, and the working wavelength and the spare wavelength of the optical signal input from the input highway are set to desired working wavelengths by the first to third stage optical switches. Alternatively, or when a failure occurs in the wavelength-multiplexed optical transmission line, the wavelength of the optical signal flowing through the wavelength-multiplexed optical transmission line is converted to a spare wavelength, and the k output highways are converted. Output to a desired output highway, and the bypass section includes a second matrix and a second matrix.
One multi-wavelength selective fill on each crosspoint of the lix
The optical signal input at the spare wavelength
Select with the selection filter and use the same wavelength as above.
The optical cross connect is characterized in that it is configured to output to an optical output .