JP3471202B2 - Optical CDMA circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread modulator for performing spread modulation of a signal in the optical domain and a spread modulated optical CDMA.
The present invention relates to an optical CDMA circuit configured by a despread demodulator that despreads a signal.

[0002]

2. Description of the Related Art The optical CDMA system can realize random access or self-routing operation by a code without using an element such as an optical switch.
Therefore, application to an optical LAN or an optical switching system is under study.

FIG. 7 shows the configuration of a conventional optical CDMA circuit. In the figure, the conventional optical CDMA circuit includes short optical pulse light sources 35-1 to 35-3 and the respective short optical pulse light sources 35.
Lattice type optical circuit 36-1 connected to -1 to 35-3
~ 36-3 and each lattice type optical circuit 36-1 to 36-3
Optical star coupler 37 and optical star coupler 3 connected to
7 is composed of lattice type optical circuits 36-4 to 36-6. The lattice type optical circuit 36 has a configuration in which asymmetric Mach-Zehnder type interferometers having optical path length differences of ΔL, 2ΔL, ..., JΔL (J is a natural number) are cascaded (J = 2 in FIG. 7). The left and right lattice type optical circuits 36 sandwiching the optical star coupler 37 correspond to a spread modulator and a despread demodulator of the optical pulse signal, respectively.

Here, the lattice type optical circuits 36-1, 36
-4 shows an operation example. Lattice type optical circuit 36-1, 36
The coupling ratio of the directional couplers 38-1 to 38-6 constituting the -4 asymmetric Mach-Zehnder interferometer is set to 0.5.
The repetition frequency f (H
z) (<c / (2 ^J nΔL), where c is the speed of light and n is the refractive index of the waveguide), a 2 ^J optical pulse train (in the time frame of 1 / f (sec) ( Cycle Δt (= nΔL
/ C)) is newly generated and the code sequence is configured. This code sequence includes the phase information of the phase shifters 39-1 and 39-2 of the lattice type optical circuit 36-1. When this encoded optical pulse train is incident on the opposing lattice type optical circuit 36-4 via the optical star coupler 37, each optical pulse is separated into 2 ^J optical pulses, and then coherent electric field components are added. Be seen. The phase shifters 39-3 and 39-4 of the lattice type optical circuit 36-4 are set by the phase shifter 39.
When the decoding conditions are satisfied for -1, 39-2, the optical power is concentrated in the center of the optical pulse for decoding, but when the setting is different from the decoding condition, the incident coded pulse train is further It is spread in time and no decoding is done.

FIG. 8 (a) is an incident light pulse train, and FIG. 8 (b) is J
= 2, the generated code sequence after passing through the spread modulator, FIG.
8C shows an output result when the setting of the despread demodulator satisfies the decoding condition, and FIG. 8D shows an output result when the setting of the despread demodulator does not satisfy the decoding condition. Note that this figure shows the effect of one pulse of the incident light pulse train for simplicity.

[0006]

In the conventional demodulation processing of the optical CDMA circuit, side lobe components are generated around the decoded signal light pulse even if the decoding condition is satisfied, and the S / N ratio on the receiving side is generated. There was a problem of deterioration. Also, in the case of non-decoding, an optical pulse train is generated, which deteriorates the S / N ratio of the decoded optical signal. This is because the autocorrelation characteristic and the cross-correlation characteristic deviate from the ideal state in the CDMA spread modulator and the despread demodulator, respectively.

An object of the present invention is to provide an optical CDMA circuit capable of reducing unnecessary sidelobe components of a decoded signal light pulse and reducing the output level of a non-decoded signal light pulse.

[0008]

An optical CDMA circuit of the present invention comprises a spread modulator for performing spread modulation of a signal in an optical region and a despread demodulator for performing despread demodulation of a spread modulated optical CDMA signal. Further, the despread demodulated decoded signal light pulse is branched into two, and the optical path length of one of the decoded signal light pulse is
Conditioned and amplified, or either decoded signal optical pulse
The optical signal is converted into an electrical signal and the electrical signal is used to control optical power.
By driving the light source for the lens, the other
Control with predetermined level synchronized with decoded signal light pulse
A control light pulse generating means for generating a light pulse and two branches
The other decoded signal light pulse and this decoded signal light pulse
Input a control light pulse having a predetermined level to be synchronized,
Of the control light pulse with respect to a predetermined level or more of the decoded signal optical pulse of the decoded signal light pulse (main peak pulse)
Induces non-linear effects such as phase change, polarization rotation, optical frequency change, etc.
The main peak pulse caused by this nonlinear effect.
And an optical time division demultiplexing circuit for demultiplexing and outputting the light . Thereby, the unnecessary side lobe component contained in the decoded signal light pulse can be reduced. Further, the output level of the non-decoded signal light pulse can be reduced.

[0009]

The optical time division demultiplexing circuit is a TO
AD, optical Kerr switch, 4 light wave mixing switch, cross phase modulation switch, non-linear loop mirror (NOLM) is used, phase change, polarization rotation, optical frequency to main peak pulse by control light pulse synchronized with main peak pulse. Separation by giving changes etc. ( Claims 2 to 6 ). Also, TO
A semiconductor laser amplifier is used as a non-linear optical element arranged in a loop-shaped waveguide forming AD ( claim 7 ).

Further, as the spread modulator and the despread modulator, a lattice type optical circuit which has been used conventionally ( claim
Section 8), and optical circuit by an optical splitter and a plurality of waveguides and the phase shifter and an optical coupler having different optical path lengths (claim
9 ), an optical circuit composed of an optical demultiplexer, a plurality of waveguides, and a phase shifter and an optical multiplexer ( claim 10 ) can be used. An arrayed waveguide diffraction grating is used as the optical demultiplexer and the optical multiplexer ( claim 11 ).

[0012]

1 shows an embodiment of an optical CDMA circuit according to the present invention. In the figure, the optical CD of the present embodiment
The MA circuit includes short optical pulse light sources 11-1 to 11-3,
Spreading modulators 12-1 to 12-3 and optical star coupler 13
And the despread demodulators 14-1 to 14-3 similar to the conventional optical CDMA circuit, and the decoded signal optical pulses output from the despread demodulators 14-1 to 14-3. Of these, threshold elements 20-1 to 20-3 for outputting decoded signal light pulses (hereinafter, referred to as "main peak pulse") each having a predetermined level or higher are provided.

The threshold element 20 utilizes an optical time division demultiplexing circuit for separating an optical pulse synchronized with a control optical pulse from a time division multiplexed optical pulse train. The optical signal is provided with control light pulse generation means for generating a control light pulse having a predetermined level in synchronization with the despread demodulated decoded signal light pulse, and the despread demodulated decoded signal light pulse is controlled in the optical time division demultiplexing circuit. In this configuration, an optical pulse is input and the main peak pulse is separated.

FIG. 2 shows a configuration example of the threshold element 20. Here, as an optical time division demultiplexing circuit, TOAD (Terahe
An example of configuration using rtz Optical Asymmetric Demultiplexer) is shown.

The threshold element 20 includes a directional coupler 21-1 for branching the decoded signal light pulses 1a, 1b, 1c output from the despread demodulator 14 into two and a directional coupler 21-2.
A loop-shaped waveguide 24 in which two output ports are connected in a loop, and polarization beam splitters 22-1 and 22-2 and a nonlinear optical element 23 are arranged in the loop, and an optical amplifier 2
5 and a TE / TM mode converter 26. The nonlinear optical element 23 is arranged at a position deviated from the midpoint 27 of the loop-shaped waveguide 24 by Δx.

Here, one output port of the directional coupler 21-1 and one input port of the directional coupler 21-2 are connected via the input side waveguide 28, and the directional coupler 21 is connected.
The output waveguide 29 is connected to the other input port of -2.

The other output port of the directional coupler 21-1 and the input port of the polarization beam splitter 22-1 are connected via an optical amplifier 25, a TE / TM mode converter 26 and a waveguide 30. . That is, the directional coupler 21-1, the optical amplifier 25, the TE / TM mode converter 2
6 and the waveguide 30 are synchronized with the decoded signal light pulses 1a to 1c and control light pulses 2a to 2c having a predetermined level.
Is a control light pulse generating means for generating. The length of the waveguide 30 is determined by the decoded signal light pulses 1a to 1c.
It can be adjusted to an appropriate length for synchronization with. Also,
It is also possible to separately prepare a light source for the control light pulse and synchronize the output control light pulse with the decoded signal light pulse.

The TE-TM mode converter 26 sets the polarizations of the decoded signal light pulses 1a to 1c and the control light pulses 2a to 2c such that one is in the TE mode of the waveguide and the other is in the TM mode and orthogonal to each other. It Thereby, the control light pulses 2a to 2c inputted from the polarization beam splitter 22-1 to the loop-shaped waveguide 24 can be separated and taken out from the polarization beam splitter 22-2. In addition,
The TE-TM mode converter 26 may be replaced by a wavelength converter to change the wavelengths of the control light pulses 2a to 2c, and a WDM coupler may be used to combine and demultiplex the decoded signal light pulse. Further, the polarization beam splitter 22-2 and the WDM coupler corresponding thereto may be arranged at the subsequent stage of the output side waveguide 29.

The directional couplers 21-1 and 21-2 are realized by a configuration in which two waveguides are arranged close to each other, a configuration in which one or more symmetrical Mach-Zehnder interferometers are connected in series, and the like. To be done. The optical amplifier 25 is realized by a rare earth element-doped optical fiber amplifier, a rare earth element-doped waveguide amplifier, a semiconductor laser amplifier, or the like. The non-linear optical element 23 is realized by a semiconductor laser amplifier or the like (claim 4).

The operation of TOAD will be described below with reference to FIGS. 2 (a) and 2 (b). In FIG. 2, the directional coupler 2
If the coupling ratio of 1-2 is set to 0.5, the loop waveguide 2
The decoded signal light pulses 1a to 1c input to 4 are divided into clockwise light and counterclockwise light with equal intensity. When the clockwise light and the counterclockwise light return to the directional coupler 21-2 again and have the same phase, the input-side waveguide 28.
And is transmitted to the output side waveguide 29 when the phases are different from each other.

The decoded signal light pulse 1b is the main peak pulse. The control light pulse 2b is synchronized with this main peak pulse and is set by the optical amplifier 25 to a level sufficient to change the refractive index of the nonlinear optical element 23. At this time, the control light pulses 2a and 2c are set to a level that does not change the refractive index of the nonlinear optical element 23.

[0022] Here, the bit interval of the decoded optical signal pulse 1 a to 1 c T _b, the time division multiplex separation interval T _f, tau _r a rise time of the refractive index change due to control light pulse 2b of the nonlinear optical element 23, When the fall time is τ _f , the relationship of τ _r <T _b << τ _f <T _f is established. At this time, when the control light pulse 2b that has entered the loop-shaped waveguide 24 from the polarization beam splitter 22-1 propagates clockwise and reaches the nonlinear optical element 23, the nonlinear optical element 23 has a high refractive index with a fast rise time. A sudden change occurs and then relaxes for a long time. When the control light pulse 2b reaches the nonlinear optical element 23, the demodulated signal light pulses 1a, 1b, and 1c propagating clockwise are after passing through the nonlinear optical element 23, before passing, and before passing, respectively.
Demodulated signal light pulses 1a, 1b, 1 propagating counterclockwise
c is after passing through the nonlinear optical element 23, after passing, and before passing.

Therefore, neither the clockwise or counterclockwise decoded signal light pulse 1a is subjected to the phase shift due to the change in the refractive index of the nonlinear optical element 23. The clockwise decoded signal light pulse 1b undergoes a phase shift, but the counterclockwise decoded signal light pulse 1b does not undergo a phase shift. Further, both the clockwise and counterclockwise decoded signal light pulses 1c undergo a phase shift. As a result, the decoded signal light pulse 1b which is the main peak pulse is transmitted to the output side waveguide 29, and the decoded signal light pulses 1a and 1c which are the side lobe components are reflected to the input side waveguide 28 to separate them. You can If the velocity of the optical pulse propagating through the looped waveguide 24 is ν (= c / n), the switching gate time Δτ is Δτ = 2Δx / ν (JPSokoloff et al., “A Terahertz Optical A
symmetric Demultiplexer (TOAD) ", IEEE Photonics Te
chnology Letters, vol.5, no.7, pp.787-790, July, 1
993).

(Another Configuration Example of Threshold Element 20) Threshold Element 2
0 uses the optical time division demultiplexing circuit as described above,
The main peak pulse is separated from the decoded signal light pulse that has been subjected to despread demodulation. In addition to TOAD, this optical time division demultiplexing / demultiplexing circuit includes an optical Kerr switch, a four-wave mixing switch, a cross phase modulation switch, a non-linear loop mirror (NOLM), and the like can be used. Hereinafter, each will be briefly described.

The optical Kerr switch changes the polarization direction of the signal light pulse temporally overlapping with the control light pulse by 90 degrees by the Kerr effect of the control light pulse, and only the component (optical peak pulse) in which the polarization direction changes. Is separated by a polarization beam splitter (T. Morioka et al., "Ultra
fast all-optical switching utilizing the opticalKe
rr effect in polarization-maintaining single-mode
fibers ", IEEE J. Select. Areas. Commu., vol.6, pp.1
186-1198, 1988).

The four-wave mixing switch causes a frequency shift of the signal light pulse temporally overlapping the control light pulse due to the four-light wave mixing process between the control light pulse and the signal light pulse, and this component (light peak pulse) is generated. It is separated by an optical frequency filter (PAAndrekson et al., "16G
b / s all-optical demultiplexing using four-wave mix
ing ", Elect. Lett., vol.27, pp.922-924, 1991).

In the cross phase modulation switch, the signal light pulse train undergoes a frequency shift which changes with time through cross phase modulation with the control light pulse, and an optical frequency for extracting the frequency of a desired signal light pulse (light peak pulse). It is separated by a filter (T. Morioka et al., "An ultrafas
t polarization-independent optical demultiplexerut
ilizing optical carrier frequency shift through cr
oss-phase modulation ", Elect.Lett., vol.28, pp.107
0-1072, 1992).

The nonlinear loop mirror (NOLM) is a TO
A loop mirror (Sagnac interferometer) configuration is used as in the case of AD, but the entire loop is configured by a non-linear optical element such as an optical fiber instead of installing a non-linear optical element in a part of the loop. The signal light pulse is split into both-direction light by the directional coupler and propagates, is again coupled by the directional coupler, and returns to the input side. Here, when a control light pulse is input in one direction, only the signal light pulse temporally overlapped in the same direction as this control light pulse undergoes phase shift due to cross-phase modulation, and under appropriate conditions, the two light beams are rotated. The phase difference can be π.
This signal light pulse (optical peak pulse) is separated as transmitted light (NJDoran et al., "Nonlinear-optical loop m
irror ", Opt. Lett., vol.13, pp.56-58, 1988).

(Structural Examples of Spreading Modulator and Despreading Modulator) Next, structural examples of the spreading modulators 12-1 to 12-3 and the despreading demodulators 14-1 to 14-3 shown in FIG. 1 will be described. To do.

First, as the spread modulators 12-1 to 12-3 and the despread demodulators 14-1 to 14-3, the lattice type optical circuits 36-1 to 36-6 shown in FIG. 7 can be used. Here, the phase shift values of the phase shifters 39-1 to 39-4 of the lattice type optical circuits 36-1 and 36-4 are φ ₁ to
φ ₄

When a short optical pulse having a repetition frequency f (Hz) is incident on the lattice type optical circuit 36-1, an optical pulse train having a period Δt (= nΔL / c) is generated as shown in FIG. 3 (a),
Phase information of the phase shifters 39-1 and 39-2 (for example, φ ₁
= Φ ₂ = π) is formed. This coded optical pulse train is incident on the opposing lattice type optical circuit 36-4 via the optical star coupler 37 (13). Here, the phase shifters 39-3 and 39- of the lattice type optical circuit 36-4.
When the setting of 4 satisfies the decoding condition for the phase shifters 39-1 and 39-2 (for example, φ ₃ = φ ₄ =
0), as shown in FIG. 3B, the optical power is concentrated in the center of the optical pulse for decoding, but side lobe components also appear.
On the other hand, if the setting is different from the decoding condition (for example, φ ₃ =
In (π, φ ₄ = 0), the incident coded pulse train is further spread in time as shown in FIG. 3 (c) and is not decoded. Note that FIG. 3 shows the effect of one pulse of the incident light pulse train for simplicity.

Therefore, by setting the switching gate time Δτ as Δτ <Δt using the threshold element 20 described above, the output optical pulse of the lattice type optical circuit 36-4 shown in FIG. Only the main peak pulse from which sidelobe components have been removed as in d).

On the other hand, when the decoding condition is not satisfied, the output optical pulse of the lattice type optical circuit 36-4 becomes as shown in FIG. 3 (c), and thereafter, the refractive index of the nonlinear optical element 23 of the threshold element 20 is changed. The control light pulse for changing is not generated, the output light pulse of the lattice type optical circuit 36-4 is reflected by the threshold element 20, and the output light intensity of the threshold element 20 is shown in FIG.
It becomes 0 like (e).

By using such a threshold element 20, the unnecessary side lobe component of the decoded signal light pulse can be reduced and the output level of the non-decoded signal light pulse can be reduced, and the S / N on the receiving side can be reduced. The ratio can be improved.

4 and 5 show spread modulators 12-1 to 12-1.
12-3 and other examples of the configurations of the despread demodulators 14-1 to 14-3. Since the spread modulator and the despread demodulator all have the same configuration, only one of them will be shown.

Spreading modulator (despreading demodulator) shown in FIG.
Is the input / output of the 1 × 4 optical branching device 41 and the 4 × 1 optical coupler 42, and the optical path length difference is ΔL, 2Δ with respect to one waveguide.
The configuration is such that four waveguides of L and 3ΔL are connected, and the phase shifters 43-1 to 43-4 are inserted into the respective waveguides.
Here, in the optical branching device 41 and the optical coupling device 42, an optical star coupler, an MMI coupler, a 2 × 2 directional coupler are cascaded in multiple stages, a Y branch waveguide is cascaded in multiple stages, etc. Can be used.

When an optical pulse train is incident on the diffusion modulator and the despreading demodulator having such a configuration, the optical pulse train is diffusion-modulated on the time axis due to the delay time difference of the waveguide as in the lattice type optical circuit shown in FIG. And despread demodulation can be performed. Similarly, by combining the set values of the phase shifter, it is possible to decode and non-decode the spread-modulated optical CDMA signal.

Spreading modulator (despreading demodulator) shown in FIG.
Is a configuration in which two arrayed waveguide diffraction gratings 51-1 and 51-2 are connected symmetrically via phase shifters 52-1 to 52-4. Each arrayed-waveguide diffraction grating corresponds to the input waveguide 5
3, an input side slab waveguide 54, an array waveguide 55, an output side slab waveguide 56, an output waveguide 57,
It functions as an optical demultiplexer and an optical multiplexer, respectively. The optical pulse input from the input waveguide 53 of the arrayed waveguide diffraction grating 51-1 is demultiplexed into the output waveguide 57 for each optical frequency component, and the corresponding phase shifters 52-1 to 52-2 are provided.
The signal is input from the output waveguide 57 of the arrayed waveguide diffraction grating 51-2 via -4, and is multiplexed and output to the input waveguide 53.

When an optical pulse train is made incident on the spreading modulator and the despreading demodulator having such a configuration, the spreading modulation and the despreading demodulation of the optical pulse train can be performed on the optical frequency axis. Similarly, by combining the set values of the phase shifter, it is possible to perform decoding and non-decoding of the spread-modulated optical CDMA signal.

When a silica glass waveguide is used as each waveguide portion of the optical CDMA circuit of the present invention shown above, the hybrid integration of the silica glass waveguide and the semiconductor laser amplifier (nonlinear optical element 23) is as follows. PLC whose cross section is shown in FIG.
(Planar Lightwave Circuit) This is done using the platform. The formation process is as follows.

After the Si terrace region 62 is formed on the Si substrate 61 by anisotropic etching, the SiO ₂ lower cladding layer 6 is formed by a flame deposition method that completely fills the Si terrace region 62.
Form 7. Next, flattening polishing is performed to form a height reference plane when the semiconductor laser amplifier 65 is mounted.
The surface of the terrace region 62 is exposed. Subsequently, the SiO ₂ height adjusting layer 68 and the GeO _{2 are} adjusted so that the height of the core of the optical waveguide and the height of the active layer 66 of the semiconductor laser amplifier 65 match.
A SiO ₂ core layer 69 doped with is added as a dopant. Then, in order to obtain the optical circuit patterns as shown in FIGS. 1, 2, 4, 5, and 7, the core layer is etched to form a core portion. Further, a SiO ₂ upper clad layer 70 is deposited to form a waveguide portion. Next, the portion to be the mounting portion of the semiconductor laser amplifier 65 is etched to expose the surface of the Si terrace region 62. Finally, an insulating SiO ₂ film is formed on the surface of the Si terrace region 62, an Au electric wiring 63 and an AuSn solder pattern 64 are formed thereon, and a semiconductor laser amplifier 65 is mounted.

The phase shifter based on the thermo-optic effect is formed by depositing a thin film heater and electric wiring on a predetermined waveguide. The waveguide portion of the optical CDMA circuit of the present invention is not limited to the glass waveguide, but may be a dielectric waveguide,
It can be realized by using a semiconductor waveguide, a polymer waveguide, or the like. It can also be realized using a hybrid integrated structure that combines several types of waveguides.

[0043]

As described above, the optical CDM of the present invention is used.
The circuit for A is a threshold element connected to the output side of the despread demodulator, and outputs a decoded signal light pulse (main peak pulse) of a predetermined level or higher among the decoded signal light pulses subjected to despread demodulation. Thereby, the unnecessary side lobe component contained in the decoded signal light pulse can be reduced. Further, the output level of the non-decoded signal light pulse can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a CDMA circuit of the present invention.

FIG. 2 is a diagram showing a configuration example of a threshold element 20.

FIG. 3 is a diagram showing an operation example of a CDMA circuit of the present invention.

FIG. 4 is a diagram showing another configuration example of a spread modulator and a despread demodulator.

FIG. 5 is a diagram showing another configuration example of a spread modulator and a despread demodulator.

FIG. 6 is a cross-sectional view of a case where a silica glass waveguide is used for a waveguide portion of a CDMA circuit of the present invention and a semiconductor laser amplifier is hybrid-integrated as a nonlinear optical element.

FIG. 7 is a diagram showing a configuration of a conventional CDMA circuit.

FIG. 8 is a diagram showing an operation example of a conventional CDMA circuit.

[Explanation of symbols]

11 Short Optical Pulse Light Source 12 Spreading Modulator 13 Optical Star Coupler 14 Despreading Demodulator 20 Threshold Element 21 Directional Coupler 22 Polarizing Beam Splitter 23 Nonlinear Optical Element 24 Loop Waveguide 25 Optical Amplifier 26 TE / TM Mode Converter 27 Midpoint of loop-shaped waveguide 28 Input-side waveguide 29 Output-side waveguide 35 Short optical pulse light source 36 Lattice type optical circuit 37 Optical star coupler 38 Directional coupler 39 Phase shifter 41 Optical splitter 42 Optical coupler 43 Phase shifter 51 Array Waveguide Diffraction Grating (Optical Demultiplexer, Optical Multiplexer) 52 Phase Shifter 53 Input Waveguide 54 Input Side Slab Waveguide 55 Array Waveguide 56 Output Side Slab Waveguide 57 Output Waveguide 61 Si Substrate 62 Si Terrace Area 63 Au electrical wiring 64 AuSn solder pattern 65 semiconductor laser amplifier 66 active layer 67 SiO ₂ lower clad layer 68 SiO ₂ height adjusting layer 69 SiO ₂ core layer 70 SiO ₂ upper clad layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01S 3/108 G02B 6/12 F H04B 10/04 6/28 B 10/06 10/142 10/152 H04J 14/04 14 / 06 (56) References JP-A-9-98156 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 G02B 6/12 G02B 6/14 G02B 6/293 G02F 1/35 H01S 3/108

Claims (11)

(57) [Claims] 1. A spread modulator that performs spread modulation of a signal in an optical region, and spread-modulated optical CDMA (Code Division Mult).
iple Access: code division multiple access) In an optical CDMA circuit provided with a despread demodulator for despread demodulating a signal, the despread demodulated decoded signal light pulse is branched into two, and
Either adjust the optical path length of the decoded signal light pulse and amplify it,
Or one of the decoded signal light pulse is converted into an electric signal
Drive the control light pulse light source using the electrical signal.
By doing so, the other decoded signal optical pulse
A control light pulse with a predetermined level that is synchronized with
Control optical pulse generating means, the other two decoded signal light pulses, and the decoded signal.
Control light having a predetermined level synchronized with the signal light pulse
Enter the pulse, for a given level or more of the decoded signal light pulse (main peak pulse) of the decoded signal pulse
Phase change by the control light pulse, polarization rotation, optical frequency
Inducing a non-linear effect such as a number change and receiving this non-linear effect
Optical time division that outputs the main peak pulse separated in time
A circuit for optical CDMA, comprising a demultiplexing circuit. 2. The optical time division demultiplexing circuit connects a directional coupler and a loop-shaped waveguide to form a loop mirror, and inputs the control light pulse to the loop-shaped waveguide to propagate in one direction. And outputting the decoded signal light pulse to the directional coupler by inserting a nonlinear optical element whose refractive index is changed by the control light pulse at a position displaced from the midpoint of the loop-shaped waveguide. It is input and propagated in the loop-shaped waveguide bidirectionally and re-inputted to the directional coupler, and the main peak pulse and another optical pulse in which a phase difference is generated in the decoded signal optical pulse due to the non-linear effect 2. The optical CDMA circuit according to claim 1, wherein the TOAD is separated into different ports of the directional coupler. 3. The optical time division demultiplexing circuit, by the nonlinear action (optical Kerr effect) by the control light pulse,
Of the decoded signal light pulse, an optical Kerr medium that changes its polarization direction with respect to the main peak pulse that temporally overlaps with the control light pulse, and a polarized beam that separates only the component (main peak pulse) whose polarization direction has changed The optical CDMA circuit according to claim 1, which is an optical Kerr switch configured by a splitter. 4. The optical time division demultiplexing circuit is configured to control the time and the control light pulse of the decoded signal light pulse by the non-linear action (four light wave mixing process) between the control light pulse and the decoded signal light pulse. Is a four-wave mixing switch composed of a non-linear optical medium that causes a frequency shift with respect to main peak pulses that overlap each other and an optical frequency filter that separates only the frequency-shifted component (main peak pulse). The optical CDMA circuit according to Item 1. 5. The optical time division demultiplexing circuit temporally compares with the control light pulse of the decoded signal light pulse by the non-linear action (mutual phase modulation) between the control light pulse and the decoded signal light pulse. 7. A cross-phase modulation switch composed of a non-linear optical medium that causes a frequency shift with respect to the main peak pulse overlapping with each other, and an optical frequency filter that separates only the frequency-shifted component (main peak pulse). 1. The optical CDMA circuit described in 1. 6. The optical time-division demultiplexing circuit connects a directional coupler and a loop-shaped waveguide composed of a nonlinear optical element to form a loop mirror, and inputs the control light pulse to the loop-shaped waveguide. And propagating in one direction to output, the decoded signal light pulse is input to the directional coupler to propagate the looped waveguide bidirectionally and re-input to the directional coupler, The main peak of the decoded signal light pulse, which propagates in the same direction as the control light pulse in the same direction in time, undergoes a phase shift due to the non-linear effect (mutual phase modulation), and causes a phase difference in the directional coupler. The optical CDMA circuit according to claim 1, wherein the optical CDMA circuit is a non-linear loop mirror (NOLM) that separates a pulse and another optical pulse into different ports of the directional coupler. 7. The optical CDMA according to claim 2, characterized in that a semiconductor laser amplifier as a nonlinear optical element disposed in the loop-shaped waveguides constituting the TOAD
Circuit for. 8. The spread modulator and the despread demodulator have a configuration in which one asymmetric Mach-Zehnder interferometer or a plurality of asymmetric Mach-Zehnder interferometers having different optical path lengths of two waveguides are cascade-connected, 8. The optical CDMA according to claim 1, wherein at least one of the two waveguides of each asymmetrical Mach-Zehnder interferometer is provided with a phase shifter for changing an optical phase. Circuit for. 9. A spread modulator and a despread demodulator each include an optical branching device for branching input light into a plurality of optical paths, and a plurality of optical paths having different optical path lengths for propagating the respective lights branched by the optical branching device. A waveguide, a plurality of phase shifters that change the optical phase of each light propagating through the plurality of waveguides, and an optical coupler that couples each light propagating through the plurality of waveguides and the plurality of phase shifters Any one of claims 1 to 7 characterized in that
The circuit for optical CDMA according to claim 1. 10. A spread modulator and a despread demodulator are provided with an optical demultiplexer for demultiplexing input light into a plurality of optical frequency components, and light of each optical frequency component demultiplexed by the optical demultiplexer. A plurality of waveguides that propagate, a plurality of phase shifters that change the optical phase of each optical frequency component that propagates in the plurality of waveguides, and an optical frequency component that propagates in the plurality of waveguides and the plurality of phase shifters 9. An optical CDMA circuit for multiplexing the light according to claim 1, wherein the optical CDMA circuit according to any one of claims 1 to 7 . 11. An array waveguide diffraction grating is symmetrically arranged as an optical demultiplexer and an optical multiplexer, and a phase shifter is connected between the output waveguides of each array waveguide diffraction grating. The optical CDMA circuit according to claim 10 .