JP3303271B2 - Optical fiber contrast method of branch optical line - 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 fiber contrast system of a branch optical line, and more particularly, to a branch optical line which is promising for providing video distribution services and the like at low cost, and a core used for construction and maintenance thereof. The present invention relates to a line contrast method and a technique effective when applied to the contrast method.

[0002]

2. Description of the Related Art When constructing and maintaining an optical fiber communication network, it is necessary to know the individual identification number of an optical fiber core in a cable or at a customer's house at a work site. This operation is referred to as a cord control, and is usually performed by a method as shown in FIG . In other words, the signal light for the core wire comparison is input from the signal light source for the core wire control 7 ′ installed on the upstream side of the optical fiber 1 ′ requiring the control via the signal light incidence means 8 for the fiber core. On the downstream side of the optical fiber 1 ′, the optical fiber is bent by using the optical fiber reference signal light receiving means 9, the optical fiber signal light is emitted outside the optical fiber, and this is detected.

Here, an optical fiber coupler, a waveguide type directional coupler, or the like is used as the optical fiber reference signal incident means 8, or the optical fiber reference signal is directly input from the end face of the upstream optical fiber. Light is incident.

[0004] A signal light source for controlling the cords is a light source such as a laser diode (LD) or a light emitting diode (LED) having a longer wavelength than a communication light source, which is subjected to frequency modulation in an audible range of about 270 Hz. Is used.

The bending radius is selected so that the signal light receiving means 9 does not affect the wavelength light for communication and efficiently emits only the signal light for fiber contrast.
In this way, the core line comparison is performed by detecting the core line contrast signal sent from the upstream side of the optical fiber 1 'by the worker on the downstream side.

On the other hand, as an optical communication system for providing video distribution services and the like at low cost, construction of a branch optical network is expected to be promising. FIG. 8 shows a basic configuration of a branch optical line network. A signal transmitted through an upstream optical fiber 1 is converted into n number of downstream optical fibers 3 by a wavelength-independent optical branching element 4.
.., 3-n. Multimedia communication experiments using such a branch optical network have been conducted in cooperation with the New Generation Communication Network Utilization Association, NTT, the Ministry of Posts and Telecommunications, and others.
It has been implemented in the Keihanna area.

[0007]

FIG. 7 and FIG.
As is apparent from FIG. 8 , when the conventional optical fiber contrast method is applied to the branch optical network, the optical signal for optical fiber contrast is transmitted from the wavelength-independent optical branching element 4 to the downstream optical fibers 3-1 to 3-n. Since they are almost equally distributed, the downstream optical fibers cannot be individually distinguished and compared. Therefore, at the site, the core is compared by relying on the mark attached to the downstream optical fiber in the immediate vicinity of the optical branching element, and at the end of the downstream optical fiber, the core cannot be virtually compared. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical fiber contrast system which enables optical fiber contrast in an arbitrary downstream optical fiber of a branch optical network.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

The outline of a typical invention among the inventions disclosed in the present application will be briefly described as follows.

[0011] (1) wherein one upstream optical fiber, the downstream optical fiber a plurality of, and the upstream-side optical fiber birefringence
Light branching means for coupling several downstream optical fibers, fiber-contrast signal light incidence means for receiving the fiber-contrast signal light provided on the upstream optical fiber, and the core control signal light is radiated out of the optical fiber made from the signal light receiving means to detect, the light branching means, wave communication
Pass long light through all downstream optical fibers and
A plurality of downstream optical fiber
The wavelength dependence of the light passing through each
Optical component, and the core contrast signal is
Switch the maintenance wavelength light at regular time intervals, and
Different unique pulses for each of the downstream optical fibers
This is a core line contrast system of a branch optical line, which is a signal train .

(2) In the above-mentioned (1), the optical fiber contrast system of the branch optical line, the optical fiber contrast signal is a signal which is different for each unique maintenance wavelength light allocated to each of the downstream optical fibers. This is an optical signal that is modulated and supplies the unique maintenance wavelength light assigned to the downstream optical fiber for each wavelength.

[0013] (3) In the above-mentioned (1) or (2), the optical fiber contrast system of the branch optical line, the means for generating the optical fiber signal for the optical fiber contrast includes all spectrums of the maintenance wavelength of the downstream optical fiber. And a band-pass tunable optical filter.

(4) In the optical fiber contrast system of any one of the above (1) to (3), the optical branching means comprises: a wavelength-independent optical branching element; An optical band-pass filter, which is provided immediately downstream of the optical branching element and passes only communication wavelength light and maintenance wavelength light unique to the downstream optical fiber.

(5) In any one of the above (1) to (3), in the optical fiber contrast system of the branch optical line, the optical branching means may be provided for each of the communication wavelength light and the downstream optical fiber. It is a wavelength-dependent optical branching element that passes only the assigned unique maintenance wavelength light.

(6) In any one of the above (1) to (5), in the optical fiber contrast system of the branch optical line, the optical fiber contrast signal light for the maintenance wavelength of the downstream optical fiber is respectively Are transmitted at different periods corresponding to the maintenance wavelengths, and the identification of the downstream optical fiber is performed based on the detected period of the optical fiber contrast signal light.

That is, according to the present invention, a different maintenance wavelength light is assigned to each of the downstream optical fibers to be compared in the branch optical line network and passed therethrough, and the identification of the assigned maintenance wavelength light is performed by a different maintenance light. The most distinctive feature is that it is distinguished from a different core reference signal array assigned to each wavelength light.

According to the above-described means, a wavelength-independent optical branching element and an optical band-pass filter are used for an optical signal incident from the upstream side, or the wavelength-independent optical branching element and the optical band-pass filter are used. The wavelength selection of the optical signal can be performed by using the wavelength-dependent optical branching element having the function of the pass filter. This makes it possible to assign different maintenance wavelength light to the downstream optical fiber of the branch optical network.

Assigning and passing different maintenance wavelength lights to each of the downstream optical fibers to be compared in the branch optical line network, and providing optical signals at different time intervals to each of the assigned maintenance wavelength lights. Thus, it is possible to identify which of the maintenance wavelength lights. Thus, the downstream optical fiber to be compared with the branch optical network can be identified.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with its embodiments (examples).

In all the drawings for describing the embodiments, parts having identical functions are given same symbols and their repeated explanation is omitted.

(Embodiment 1) FIG. 1 is a diagram showing the overall configuration of Embodiment 1 (Example 1) of the present invention, where 1 is an upstream optical fiber, 3-1 and 3-
2,..., 3-n are downstream optical fibers, 4 is a wavelength-independent optical branching element (optical branching means), 6-1, 6-2,.
6-n is an optical band-pass filter, 7 is a signal light source for reference, 8 is a signal light input means for reference, and 9 is a signal light receiving means for reference.

The wavelength-independent optical branching element (optical branching means) 4 is a coupler-type or waveguide-type optical branching element that branches the passing light regardless of the wavelength of the passing light.
This is to distribute the passing light equally.

The optical band-pass filters 6-1, 6-2,...
.., 6-n are well-known optical bandpass filters, which selectively transmit the communication wavelength and the light of the maintenance wavelength allocated to each downstream optical fiber, and block the light of the other maintenance wavelength. Is what you do.

The optical signal input means 8 for the optical fiber contrast is an optical coupler of a coupler type or a waveguide type, and inserts light of the wavelength for maintaining the upstream optical fiber.

FIG. 2 shows the signal light source 7 for the core wire contrast in FIG.
1 is a diagram showing an embodiment of the present invention, wherein 10 is a light source having a wide wavelength spectrum width, 11 is a wavelength tunable optical filter control device, and 12 is a band-pass tunable optical filter.

The wide wavelength spectrum width light source 10 is an LD or LED having a wide wavelength spectrum, and generates maintenance wavelength light.

The band-pass tunable optical filter 12 is a well-known band-pass tunable optical filter, and includes a maintenance wavelength assigned to each downstream optical fiber from the wavelength spectrum components of the wide wavelength spectrum light source 10. The light of the wavelength is selected, and a signal cycle having a different interval is generated for each maintenance wavelength light.

As shown in FIG. 1, the optical fiber contrast system of the branch optical line according to the first embodiment includes a single upstream optical fiber 1,
A plurality of downstream optical fibers 3-1, 3-2, ..., 3-
n, a wavelength-independent optical branching element (optical branching means) 4 for coupling the upstream optical fiber 1 and the downstream optical fibers 3-1, 3-2,..., 3-n; An optical fiber signal inputting means 8 provided in the upstream optical fiber 1 for inputting an optical fiber reference signal light, and radiating the optical fiber signal out of the optical fiber. And a signal light receiving means 9 for detecting the optical fiber. The optical fiber reference signal is an optical signal transmitted while the unique maintenance wavelength assigned to each of the downstream optical fibers is switched at regular time intervals. It is.

Next, the operation of Embodiment 1 (Example 1) will be described in detail. 2, from the broad wavelength spectral components of broad wavelength spectral bandwidth source 10 for emitting light continuously, by band pass type wavelength tunable optical filter 12 which receives the control by the tunable optical filter control unit 11, the downstream-side optical fiber , A plurality of maintenance wavelength light components are selected, and at the same time, signal periods with different intervals are assigned, and the assigned periodic signal lights are operated so as not to overlap with each other, thereby performing pulse code modulation. At this time, the transmission time of the selected maintenance wavelength light (hereinafter, referred to as the core control pulse signal width τ) is all equal regardless of a plurality of different maintenance wavelength light components assigned to the downstream optical fiber, In addition, the signal interval of the same maintenance wavelength light is also normalized as an integral multiple of the core control pulse signal width τ.

Here, the basis for selecting the core code reference signal lights, which are pulse-code modulated for each of the plurality of maintenance wavelength lights assigned to the downstream optical fiber, without duplication is determined by using the equation (1). explain.

[0032]

T (i, j) = 2 ^ij × (2j−1)

I is a downstream optical fiber identification number, which corresponds to a plurality of different maintenance wavelength lights allocated to the downstream optical fiber. j is the signal number when the transmission time of the core-contrast signal light is normalized by the core-contrast pulse signal width τ, T (i,
j) shows the time of the i-th downstream optical fiber and the j-th signal.
Here, any different downstream optical fiber identification numbers i,
For i ′ (i> i ′), suppose that T (i, j) = T
When (i ′, j ′) holds, the following equation (2) is obtained. The left side is an even number, and the right side is an odd number.

[0034]

2 ⁱ⁻¹ × (2j−1) = 2 ^i′−1 × (2j′−1) 2 ^{i−i ′} × (2j−1) ≠ 2j′−1

Therefore, T (i, j) ≠ T (i ′, j ′), and any different downstream optical fiber identification numbers i, i ′
, The j-th signal does not overlap at time T (i, j). Therefore, according to Equation 1, it is possible to carry out pulse code modulation of the optical fiber for reference with a different signal period for each of the plurality of different wavelengths for maintenance.

FIG. 3 shows a transmission array pattern of the signal light for the optical fiber contrast incident on the wavelength-independent optical branching element 4 obtained by the equation (1). That is, the first signal is converted to the wavelength λ.
One light ( i = 1 in FIG. 3) and the second signal are converted into light of wavelength λ2 (FIG. 3).
i = 2 ), the third signal is wavelength λ1 light, and the fourth signal is wavelength λ3
Light ( i = 3 in FIG. 3),..., The wavelength λ1 light is twice as long as the core control pulse signal width τ, and the wavelength λ2 light is four times as long as the core control pulse signal width τ. , And the wavelength λ3 light is transmitted at a cycle eight times as large as the core control pulse signal width τ. In the following, the signal arrangement of a plurality of different maintenance wavelength lights assigned to the downstream optical fiber is changed at a period of ²ⁱ times the core control pulse signal width τ according to the number n of branches to be similarly identified.

Next, in the wavelength-independent optical branching element 4, the signal light for optical fiber contrast is distributed to the downstream optical fibers 3-1, 3-2,..., 3-n regardless of the wavelength. After
The light passes through the optical band-pass filters 6-1, 6-2, ..., 6-n.

FIG. 4 shows the optical band-pass filters 6-1 and 6--6.
2, 6-3 shows the light transmission characteristics. That is, the thin line indicates the transmission characteristics of the optical bandpass filter 6-1, and selectively transmits the light of the communication wavelength λs and the light of the maintenance wavelength λ1, and the light of the other maintenance wavelengths λ2 and λ3. Cut off. Similarly, the medium and thin lines indicate the transmission characteristics of the optical bandpass filter 6-2, and selectively transmit the light having the communication wavelength λs and the maintenance wavelength λ2, and the other maintenance wavelengths λ1 and λ2.
Blocks light such as λ3.

It is known that such characteristics shown in FIG. 4 can be designed and created with high accuracy by using, for example, a fiber grating using the photochromic effect.

[0040] Therefore, the signal sequence of the core control signal light transmitted through the optical band pass filter, i = 1, 2 of FIG. 3,
3,... That is, the signal light for the core wire contrast that has passed through the optical band-pass filter 6-1 has the wavelength λ1
Is extracted, and the light of other wavelengths λ2, λ3,... Is cut off, so that the signal light for the core line contrast of the component of wavelength λ1 is obtained as shown by i = 1 in FIG. Therefore, in FIG. 1, when the optical fiber is bent by the optical fiber signal receiving means 9 further downstream of the optical bandpass filter 6-1, the optical fiber having a period twice as long as the optical fiber pulse signal width τ is obtained. The control signal light is obtained, and it is determined that the core number is 1.

[0041] Similarly, core control signal light that has passed through the optical band pass filter 6-2, only component of the wavelength λ2 can pass, as shown in i = 2 in Figure 3, core control pulse signal A signal light for a core line reference having a period four times the width τ is obtained.
Therefore, if the optical fiber is bent by the optical fiber signal receiving means 9 further downstream than the optical bandpass filter 6-2, the optical fiber having a period four times as long as the optical fiber pulse signal width τ is obtained. The signal light is extracted, and it is determined that the core number is 2.

[0042] Hereinafter, by using Equation 1, Ri Do allow cord control for the optical path of the branch number n, the i-th downstream optical fiber 3-i connected to the optical bandpass filter 6 When the optical fiber is bent by the optical fiber reference signal receiving means 9 on the further downstream side after passing through -i, the optical fiber signal having a period of 2 ⁱ times the optical fiber pulse signal width τ is extracted. Then, it is determined that the cord number is i-th.

As shown in FIG. 4, all the optical band-pass filters are designed to transmit the communication wavelength light having the wavelength λs without fail, and the signal light receiving means 9 for comparing the optical fiber with the core is used. The bending applied to the fiber is designed not to affect the communication wavelength light.

Here, it is special to use only a periodic signal that is an integral multiple of the fiber-contrast pulse signal width τ as a fiber-contrast signal for discriminating which of a plurality of different downstream optical fibers to use. This is a completely simple method that does not require a signal detection technique or a discrimination technique using a simple trigger signal, or a complicated pulse coding and decoding technique of the optical fiber for optical fiber contrast.

(Embodiment 2) Next, Embodiment 2 (Example 2) of the present invention will be described in detail. The second embodiment has the same configuration, operation and effects as those of the first embodiment, except for the points described below.

FIG . 5 shows the overall configuration of the second embodiment of the present invention, where 1 is an upstream optical fiber, 3-1, 3-2,.
3-n is a downstream optical fiber, 5 is a wavelength-dependent optical branching element, 7 is a signal light source for reference, 8 is a signal light input means for reference, and 9 is a signal light receiving means for reference. Show.

FIG . 6 shows an embodiment of the wavelength-dependent optical branching element 5, wherein 1 is an upstream optical fiber, 2 is a signal light input fiber for optical fiber reference, 3-1, 3-2,. …, 3-
n is a downstream optical fiber, 5 is a wavelength-dependent optical branching element, 1
3 is an arrayed waveguide diffraction grating, 14 is a communication wavelength light input waveguide, 15 is a signal light output waveguide, 16 is a signal light input waveguide for core fiber contrast, 17 is a slab waveguide, and 18 is a dielectric multilayer film. Reference numeral 19 denotes a quarter-wave plate, and reference numeral 20 denotes a WDM coupler.

The wavelength-dependent optical branching element 5 shown in FIG . 6 guides the communication wavelength light input from the upstream optical fiber 1 to the communication wavelength light input waveguide 14 by the WDM coupler 20, After being developed in the horizontal direction, the light is distributed substantially equally to the n signal light output waveguides 15 and output to the downstream optical fibers 3-1 to 3-n.

On the other hand, the signal light for optical fiber reference input from the upstream optical fiber 1 is transmitted from the optical signal input fiber for optical fiber 2 to the optical signal input waveguide 16 for optical fiber reference via the WDM coupler 20. After being guided and developed by the slab waveguide 17 in the horizontal direction of the drawing, the light is distributed to the arrayed waveguide diffraction gratings 13 arranged in parallel. The distributed signal light for control of the optical fiber is reflected by the dielectric multilayer filter 18, again passes through the same arrayed waveguide diffraction grating 13, and passes through the slab waveguide 17.
Return to

Here, the arrayed waveguide diffraction grating 13 is designed such that the optical path length differences are equally different, so that each optical fiber for reference to the optical fiber is converted into the arrayed waveguide diffraction grating 1.
3, the phase shift is caused by the difference of the optical path length, and the slab waveguide 17 causes interference of multiple light beams. As a result, the position at which light is condensed changes according to the wavelength of the signal light for optical fiber contrast (hereinafter, the wavelength-dependent optical branching element 5 is referred to as an optical branching element with a wavelength routing function.
-based arrayed-waveguide grating circuit as optica
l splitter / router, Electronics Letters, Vol. 3, No.
9, pp. 726-729, April 1995. ").

The quarter-wave plate 19 is provided in order to eliminate the wavelength shift due to the polarization dependence of the optical signal for the optical fiber contrast.

Here, in the case of a branch optical line network of an intra-office branch type in which the wavelength-dependent optical branching element 5 is installed near the optical fiber input means 8 for optical fiber reference, the optical signal for optical fiber reference. It is also possible to replace the input means 8 with a wavelength division multiplexing (WDM) coupler 20.

As described above, the optical branching element with the wavelength routing function has the functions of the wavelength-independent optical branching element 4 and the optical bandpass filters 6-1 to 6-n described in the first embodiment. The method of allocating the unique maintenance wavelength light to the downstream optical fibers 3-1 to 3-n according to the first embodiment is different from the method of distributing the unique maintenance wavelength light to each of the downstream optical fibers. In that respect, there is essentially no difference.

However, a great advantage of the second embodiment is that the array waveguide diffraction grating 13 and the slab waveguide 17 realize a multi-beam interference phenomenon and distribute maintenance wavelength light as an optical wavelength router. Therefore, the first embodiment
It is possible to eliminate the essentially unavoidable distribution loss of the wavelength-independent optical branching element 4 described above, and to reduce the reduction in the power of the signal light for optical fiber contrast. This is advantageous in that a dynamic range of the optical fiber contrast device and the like is secured in a test during the construction and maintenance of the branch optical network.

As described above, the present invention has been specifically described based on the above-described embodiments (examples). However, the present invention is not limited to the above-described embodiments (examples) and does not depart from the gist thereof. Of course, various changes can be made.

[0056]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

In the branch optical network, the optical fiber can be individually compared at the terminal without tracing the optical fiber downstream of the optical branch element to the optical branch element. For this reason, the construction and maintenance work of the branch optical line is facilitated, and it is possible to contribute to the construction of a highly reliable and economical optical communication system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a first embodiment (Example 1) of the present invention.

FIG. 2 is a diagram showing an embodiment of a signal light source for core wire contrast in FIG. 1;

FIG. 3 shows one example of a signal light transmission array pattern according to the first embodiment .
It is a figure showing an example.

FIG. 4 is a diagram illustrating light transmission characteristics of the optical bandpass filter according to the first embodiment.

FIG. 5 shows the overall configuration of Embodiment 2 (Example 2) of the present invention .
FIG.

FIG. 6 shows one embodiment of the wavelength-dependent optical branching element according to the second embodiment.
It is a figure showing an example.

FIG. 7 illustrates a problem of a conventional optical fiber contrast method for a branched optical line.
It is a figure for clarification.

FIG. 8 is a diagram showing a basic configuration of a conventional branch optical line.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upstream optical fiber, 2 ... Signal optical signal input fiber for contrast, 3-1-3-n ... Downstream optical fiber, 4 ... Wavelength-independent optical branching element, 5 ... Wavelength-dependent optical branching element, 6-1
.About.6-n: optical band-pass filter, 7: signal light source for optical fiber contrast, 8 ... signal light incident means for optical fiber contrast, 9 ... signal light receiving means for optical fiber contrast, 10 ...
... wavelength tunable optical filter control device, 12 ... band-pass tunable optical filter, 13 ... arrayed waveguide grating, 14 ...
Communication wavelength light input waveguide, 15 ... signal light output waveguide, 1
Reference numeral 6 denotes a signal light input waveguide for reference to a cord, 17 denotes a slab waveguide, 18 denotes a dielectric multilayer film filter, 19 denotes a 波長 wavelength plate, and 20 denotes a WDM coupler.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01M 11/00 G02B 6/122 G02B 6/28 H04B 10/00

Claims (6)

(57) [Claims] 1. An upstream optical fiber, a plurality of downstream optical fibers, the upstream optical fiber, and the plurality of
Optical branching means for coupling the downstream optical fiber of the optical fiber, and a signal light incident means for the optical fiber reference provided on the upstream optical fiber for injecting the optical signal for the optical fiber contrast, and the optical fiber for the optical fiber contrast Signal light receiving means for radiating the signal light out of the optical fiber and detecting the signal light;
Pass through all downstream optical fibers and use different fixed
Each of the plurality of downstream optical fibers is provided with a maintenance wavelength light.
Wavelength-dependent optical part that is passed through so that it can be distributed
And the core contrast signal is different from the unique protection signal.
The guard wavelength light is switched at regular time intervals,
Different unique pulse signal train for each side optical fiber
A method of contrasting optical fibers of a branch optical line, characterized in that: 2. The optical fiber reference signal has a different signal modulation for each unique maintenance wavelength light assigned to each of the downstream optical fibers, and is assigned to the downstream optical fiber. The optical fiber contrast system according to claim 1, wherein the optical signal is a light signal for supplying the unique maintenance wavelength light for each wavelength. 3. The signal processing device according to claim 1, wherein the signal generation means comprises a light source having the entire spectrum of the maintenance wavelength of the downstream optical fiber, and a band-pass tunable optical filter. Item 3. An optical fiber contrast system for a branch optical line according to item 1 or 2. 4. The optical branching means is assigned to a wavelength-independent optical branching element and a communication wavelength light and the downstream-side optical fiber provided immediately downstream of the wavelength-independent optical branching element. 4. An optical band-pass filter for passing only the specific maintenance wavelength light.
6. The optical fiber contrast method of the branch optical line according to any one of the above. 5. The optical branching means is a wavelength-dependent optical branching element that passes only the communication wavelength light and the unique maintenance wavelength light allocated to each of the downstream optical fibers. 4. The optical fiber contrast system for a branch optical line according to claim 1, wherein: 6. The optical fiber reference signal light for the maintenance wavelength of the downstream optical fiber is transmitted at different periods corresponding to each maintenance wavelength, and the identification of the downstream optical fiber is detected. The method according to any one of claims 1 to 5, wherein the method is performed based on a cycle of the signal light for core fiber contrast.