JPH0119778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical multiplex circuit that transmits and receives multi-channel optical signals using a single optical fiber. It is generally desired that this type of optical multiplex circuit be inexpensive and capable of high multiplexing.

Conventionally, this type of optical multiplexing circuit has been a so-called wavelength multiplexing circuit as shown in FIG. In the figure, light emitted from a signal source 1 with a wavelength λ ₁ and a signal source 2 with a wavelength λ ₂ pass through optical fibers 7 and 8, are multiplexed via a multiplexer 3, and are output to a single optical fiber 9. be done. After long-distance signal transmission is performed by the optical fiber 9, the signal passes through the demultiplexer 4 and is again separated into light with a wavelength λ ₁ and light with a wavelength λ ₂ .
After passing through 0 and 11, photoelectric exchangers 5 and 6
The two optical signals are converted into electrical signals. Although an example of two-way multiplexing is shown here, optical three-way multiplexing circuits and optical four-way multiplexing circuits using three or four wavelengths of light are also constructed in the same way. However, in this wavelength multiplexing circuit, it is difficult to produce a light source of a desired wavelength with a high yield, and it is extremely expensive.

In addition to this type of optical multiplex circuit, the inventor of the present invention invented an optical multiplex circuit using an optical frequency filter as shown in Figure 2, as shown in Figure 2, and the applicant filed an application on the same date as the present application. ing. This optical multiplex circuit has the characteristic that it can be constructed at low cost because it does not have the problem of light sources as in wavelength multiplexing.

FIGS. 3, 4, and 5 show three basic configurations of optical frequency filters, which are the key hardware of this optical multiplexing circuit. Figures 3 and 4 were previously filed by the inventor of the present invention in Japanese Patent Application No. 57-36246 and Japanese Patent Application No. 57-36246, respectively.
This is an optical frequency filter proposed in No. 36247, and FIG. 5 is an optical frequency filter that was invented by the inventor of the present application and filed on the same date as the present application by the applicant of the present application. In these figures, the light emitting element 108 is intensity modulated at a certain frequency.
The light emitted from the optical fiber 109 passes through the optical fiber 109.
The light enters an optical frequency filter 118. If the modulation frequency is a frequency that can pass through the optical frequency filter, the modulation frequency is output from the optical frequency filter 118 to the light receiving element 117 via the optical fiber 116. Conversely, if the modulation frequency is such a frequency that it cannot pass through the optical frequency filter, the modulation frequency is not output to the light receiving element 117. In the optical frequency filter 118 shown in FIGS. 3 and 4, 111, 113, and 114 are optical fibers;
0 is an optical splitter, 112 is an optical attenuator, and 115 is an optical coupler. In addition, in the optical frequency filter shown in FIG. 5, 111 and 113 are optical fibers, 112 is an optical attenuator, and 119 is an optical directional coupler (splitter/
coupler). The optical attenuator 112 is shown in FIG.
Both of FIGS. 4 and 5 are used to adjust the frequency selectivity of the optical frequency filter, and as described above, the use thereof has been proposed by the inventor of the present application.

The operation of the optical frequency filter will be explained below using the transfer function. Transfer function G(S) using Laplace transform of optical frequency filter and frequency characteristic L
() is defined as the following equations (1) and (2).

G(S)=I ₀ (S)/Ii(S) (1) L()=20・log | G(2πj)/G(0) | (1) Here, I ₀ (S), Ii(S ) is the light intensity (light brightness) at a certain time at the output and input points of the filter expressed by Laplace transform, and is the frequency of the carrier wave carried by the light. Assuming that there is no reflection or group delay time difference, G(S) and L() are as follows.

In the case of the optical frequency filter shown in Fig. 3, G(S)=[η ₁ +η ₂・exp{(τ ₁ −τ ₂ )・S
}]・exp(−τ ₁ S)…(3) L()=20・log｜[η ² ₁ +η ² ₂ +2η ₁ η ₂ cos
{2π(τ ₁ −τ ₂ )}] ^1/2 / (η ₁ +η ₂ ) |…(4) In the case of the optical frequency filter shown in Figure 4, G(S)=η ₁ exp(−τ ₃・S) /{1−η ₄ exp
(−τ ₄ S) (5) L()=20log | (1−η ₄ )/{1+η ² ₄ −2
η ₄ cos (2πη ₄ )} ^1/2 | (6) In the case of the optical frequency filter shown in Figure 5, G(S)=η ₅ +η ₆ exp(−τ ₆ S)/{1−η ₇ ex
p(−τ ₇ S)}(7) L()=20log｜(1−η ₇ )・{(η ₆ −η ₅ η
₇ ) ² +η ² ₅ +2η ₅ (η ₆ −η ₅ η ₇ ) cos(2πτ ₆ )} ^1/2 / [(η ₅ +η ₆ −η ₅・
η ₂ )・{1+η ² ₇ −2η ₇ cos(2πη ₇ )} ^1/2 ] | (8)
However, τ ₁ to τ ₇ and η 1 to _{η 7} are shown in Figures 3, 4, and 5.
The group delay time and light transmittance of routes 101 to 107 in the figure are shown. Surffixes 1 and 2 connect the main path 101 and bypass 102 in FIG.
Reference numerals 6 and 7 respectively indicate the direct path 105, bypass 106, and feedback loop 107 in FIG. Note that equations (7) and (8) ignore the group delay time of the splitter/coupler 119 shown in FIG.

When η ₆ ≫η ₅ η ₇ and η ₇ 0, equations (7) and (8) become as follows.

G(S)=η ₅ +η ₆ exp(−τ ₆ S) (9) L()=20log | {η ² ₅ +η ² ₆ +2η ₅ η ₆ cos(2
πτ ₆ )} ^1/2 / (η ₅ +η ₆ ) | (10) When η ₆ =η ₅ η ₇ , equations (7) and (8) become as follows.

G(S)=η ₅ /{1−η ₇ exp(−τ ₇ S) (11) L()=20log | (1−η ₇ )/{1+η ² ₇ −2
η ₇ cos (2πτ ₇ )} ^1/2 | (12) Equations (9) and (11) are equivalent to equations (3) and (5), respectively, and equation (10),
(12) is essentially the same as equations (4) and (6). Therefore, the optical _frequency filter 118 _{in FIG .}
If 0, the optical frequency filter 118 of FIG. 3 is used, and if η ₆ =η ₅ η ₇ , the optical frequency filter 118 of FIG. 4 is used.
can be said to be essentially the same. As is clear from equations (4), (6), (10), and (12), τ ₂ , τ ₄ , τ ₆ , τ ₇ , that is, the third
It can be seen that the frequency characteristics of the filter differ depending on the length of the optical fiber 114 in FIG. 4 and the total length of the fiber 111 and fiber 113 in FIG. FIG. 6 shows the optical frequency filter 118 of FIG.
The frequency characteristics of τ are shown for several values of τ ₂ . Further, FIG. 7 shows the frequency characteristics of the optical frequency filter 118 of FIG. 4 for several values of τ ₄ . Further, FIG. 8 shows frequency characteristics when the optical frequency filter 118 of FIG. 5 is designed so that η ₆ ≫η ₅ η ₇ , η ₇ 0, and is shown for several τ ₆ values. FIG. 9 shows frequency characteristics when the optical frequency filter 118 of FIG. 5 is designed so that η ₆ =η ₅ η ₇ and is shown for several values of τ ₇ .

As can be seen from the above description, the optical frequency filter can discriminate the carrier frequency carried by light. That is, in FIG. 10, for example, if the optical frequency filter 118 has the configuration shown in FIG. 5 and its characteristics are τ ₇ =τ ₇₁ in FIG. 9, the intensity of the optical input 120 entering the optical fiber 121 is If it changes at a frequency of ₄₀ , like the light intensity waveform 124,
This optical input 120 passes through an optical frequency filter 118 and is output as an optical output 123 from an output fiber 122 . However, if the intensity of the optical input 120 varies with the carrier frequency ₄₂ , the optical intensity waveform 125
As such, this optical input 120 cannot pass through the optical frequency filter 118. The same thing can be said for τ ₇ = τ ₇₂ and τ ₇ = τ ₇₃ . The difference is simply that the carrier frequencies that can pass through the optical frequency filter 118 and the carrier frequencies that cannot pass are different from the case where τ ₇ =τ ₇₁ . Figure 8 can also be considered in the same way. The concept is the same in the cases of FIGS. 6 and 7. That is, for example, the first
In FIG. 0, when the frequency characteristic of the optical frequency filter 118 is τ ₂ =τ ₂₁ in FIG. 6, the optical fiber 12
The intensity of the optical input 120 entering 1 is the carrier frequency ₁₂
As shown in the optical intensity waveform 124, this optical input 120 passes through the optical frequency filter 118 and is output from the output fiber 122 as an optical output 123. However, if the intensity of the optical input 120 changes with the carrier frequency ₁₁ , as shown in the optical intensity waveform 125, this optical input 120 will pass through the optical frequency filter 11.
Can't pass 8. Note that in FIG. 10, t indicates time. Although the above description has focused on discrimination of the carrier wave frequency carried by light, it is clear from these descriptions that an optical frequency filter can generally discriminate light that has been intensity-modulated at a certain frequency.

Next, a second filter using these optical frequency filters will be developed.
The optical multiplex circuit shown in the figure will be explained. In Figure 2, n
Signals with frequencies P ₁ to Pn are respectively input to n modulators 202 via this (n≧2) signal input lines 201 . Carrier waves modulated by input signals are output from the n modulators 202, and are added by an adder 204 via a modulator output line 203. The addition result is 1
After passing through one optical fiber 205, the optical fiber is split again into n optical fibers 207 at a splitter 206. The n optical fibers 207 are connected to n optical fibers 209 via n optical frequency filter networks 208 . The first modulator combines the frequency components of the outputs of n modulators 202 at frequencies F ₁₁ ,
A combination of F ₂₁ ,...F _n1 , the second modulator has a frequency
If the n-th modulator is a combination of frequencies F ₁₂ , F ₂₂ ,...F _n2 , and similarly, the n-th modulator is a combination of frequencies F _1o , F _2o ,...F _no , the optical fibers 205 and 207 have a frequency that is a mixture of these. ingredients are present. Therefore, the frequency characteristics of the n optical frequency filter networks 208 are as follows:
F ₁₁ , F ₂₁ ,...F _n1 , the second optical frequency filter network has frequencies F ₁₂ , F ₂₂ ,...F _n2 , and similarly, the n-th optical frequency filter network has frequencies F _1o ,
If the design is such that only F _2o and F _no can pass through, the outputs of the n optical frequency filter networks 208 will have frequencies (F ₁₁ , F ₂₁ ...F _n1 ), (F ₁₂ ,
_F22 ,... _Fn2 ),...( _F1o , _F2o ,... _Fno ) are separately separated and output. That is, n modulators 202
(F ₁₁ , F ₂₁ ,...
F _n1 ), (F ₁₂ , F ₂₂ ,...F _n2 ),... (F _1o , F _2o ,...
F _no ) are transmitted through one optical fiber 205 and then transmitted again by an optical frequency filter network 208 as (F ₁₁ , F ₂₁ ,...F _n1 ), (F ₁₂ , F ₂₂ ,...F _n2 ), …
It is divided into (F _1o , F _2o ,...F _no ). In other words, FIG. 2 can be said to be an n-multiplex optical circuit network. In this case, the output section of the modulator 202 may be in an electrical output format or may be in an optical format in which electrical output is converted into optical output using a light emitting element such as a light emitting diode. If the output is electrical, the modulator output line 203 is an electric wire, and the adder 204 is an electrical adder. In the case of optical output, the modulator output line 203 is an optical fiber and the adder 204 is an optical directional coupler. When the adder 204 is an electrical adder, its output section is connected to the optical fiber 2 by a light emitting element such as a light emitting diode.
It is now possible to connect to 05. As can be seen from the above explanation, optical multiplexing circuits using optical frequency filters do not require light sources of several wavelengths unlike wavelength multiplexing, and therefore optical multiplexing circuits can be constructed at lower cost. It has characteristics.

It is generally desired that the optical multiplex circuit be capable of optical multiplexing. However, in conventional wavelength multiplexing circuits, four-way multiplexing is the limit. Further, although the frequency multiplexing circuit using the above-mentioned optical frequency filter solves the problem of the light source of the wavelength multiplexing circuit, it still has a limit of multiplexing.

It is an object of the present invention to realize a higher degree of multiplexing than conventional wavelength multiplexing circuits, and compared to a frequency multiplexing circuit using an optical frequency filter currently proposed by the inventor of the present invention, and to be explosion-proof. The object of the present invention is to provide an optical multiplex circuit that has high noise resistance, good noise resistance, and low cost per line.

To achieve this objective, according to the invention:
The optical multiplex circuit is an optical multiplex circuit that transmits and receives multi-channel optical signals in an all-optical manner, and includes a plurality of first units each including a plurality of modulators and one optical coupler connected by optical fibers. a plurality of second units each comprising a plurality of optical frequency filter networks and one optical branching unit connected by an optical fiber; and a plurality of said optical coupling units provided in said plurality of first units. one multiplexer connected to the plurality of second units by an optical fiber; one demultiplexer connected by an optical fiber to the plurality of optical splitters provided in the plurality of second units; an optical fiber connecting the demultiplexer and the one multiplexer, and the number of the plurality of first units is equal to the number of the plurality of second units, and the number of the plurality of first units is equal to the number of the plurality of second units. The number of modulators included in each of the first units is equal to the number of optical frequency filter networks included in each corresponding one of the plurality of second units.

FIG. 11 shows an embodiment of the present invention. Below, in an optical component that combines incident light from multiple optical fibers into a single optical fiber and outputs it, we will explain how all the light that enters the optical component via multiple optical fibers has the same wavelength. An optical component designed for this case is called an optical coupler. Also, an optical component designed for the case where the light entering the optical component via multiple optical fibers has different wavelengths is called a multiplexer. Designed for cases where the light entering the optical component via one optical fiber is of a single wavelength, in an optical component that divides the incident light from the source into multiple optical fibers and outputs it. This optical component is called an optical splitter. Furthermore, the light that enters the optical component via one optical fiber consists of light of different wavelengths, and the light of different wavelengths is output to multiple output optical fibers. An optical component like this is called a demultiplexer.

The optical multiplex circuit shown in FIG. 11 is equipped with a multiplexer and a demultiplexer, so it constitutes a wavelength multiplex circuit, and also includes a plurality of optical couplers, an optical splitter, and an optical frequency filter network. Therefore, a frequency multiplexing circuit using an optical frequency filter is constructed. That is, this optical multiplexing circuit has a configuration in which a wavelength multiplexing circuit and a frequency multiplexing circuit are combined.

In FIG. 11, each frequency P ₁₁ to _{P 1N} is input via N (N≧2) signal input lines 300.
signals are input to N modulators 303. Carrier waves modulated by input signals are outputted from the N modulators 303, respectively, and are coupled by an optical coupler 309 via a modulator output line 306. In this case, the output section of the modulator 303 is in an optical format in which electrical output is converted into optical output using a light emitting element such as a light emitting diode. Since it is an optical output, modulator output line 306 is an optical fiber. It is assumed that the N light emitting elements used in the modulator 303 all have the same emission wavelength λ ₁ . On the other hand, signals with frequencies P ₂₁ to P _2N are input to N modulators 304 via N (N≧2) signal input lines 301, respectively. N modulators 304
A carrier wave modulated by the input signal is outputted to the output of the modulator output line 30.
7 and are coupled by an optical coupler 310. In this case, the output section of the modulator 304 is in an optical format in which electrical output is converted into optical output using a light emitting element such as a light emitting diode. Since it is an optical output, modulator output line 307 is an optical fiber. Modulator 30
It is assumed that the N light emitting elements used in 4 have the same emission wavelength λ ₂ . Furthermore, N pieces (N≧2)
Signals with frequencies P ₃₁ to P _3N are input to N modulators 305 via signal input lines 302 , respectively. A carrier wave modulated by the input signal is outputted to the output of the N modulators 305, and is transmitted to the optical coupler 3 via the modulator output line 308.
11. In this case, the output section of the modulator 305 is in an optical format in which electrical output is converted into optical output using a light emitting element such as a light emitting diode. Since it is an optical output, modulator output line 308 is an optical fiber. It is assumed that the N light emitting elements used in the modulator 305 all have the same emission wavelength λ ₃ . Generally, the frequency P _i1 ...P _iN , (1≦i≦M, 2
≦M, i is an integer, and M is the number of wavelengths of light used in FIG. 11) signals are input to N modulators. A carrier wave modulated by the input signal is output to each modulator output. That is, the frequency components _i11 , _i12 , _i13 of the carrier wave modulated by the signal P _i1
，
...Frequency component of carrier wave modulated by signal P _i2
i21 , _i22 , _i23 ,..., and so on, and finally the signal
Frequency component _iN1 of carrier wave modulated by P _iN ,
_iN2 , _iN3 ... are output to N modulator outputs. These N modulator outputs are combined by an optical coupler and output to one optical fiber at wavelength λ _i . In other words, considering 1≦i≦M, 2≦M, the output of the optical coupler 309 has the signal P ₁₁ at the frequency ₁₁₁ ,
₁₁₂ , ₁₁₃ ,..., the signal P ₁₂ at frequencies ₁₂₁ , ₁₂₂ ,...
₁₂₃ ,..., the signal P _1N is changed in the same way to the frequency
_1N1 , _1N2 , _1N3 , ... light of wavelength λ ₁ is output. The output of the optical coupler 310 has a signal
P ₂₁ to frequencies ₂₁₁ , ₂₁₂ , ₂₁₃ ,..., signal P ₂₂ to frequencies ₂₂₁ , ₂₂₂ , ₂₂₃ ,..., and so on, P _2N
Light of wavelength λ ₂ with frequencies _2N1 , _2N2 , _2N3 , ... is output. In the same way, the signal P _M1 is sent to the output of the M-th optical coupler at frequencies _M11 , _M12 ,
The signal P _M2 is transmitted to _M13 ,... with frequencies _M21 , _M22 , _M23 ,
In the same way, the signal P _MN is changed to the frequency _MN1 ,
Light of wavelength λ _M placed on _MN2 , _MN3 , ... is output. The frequency components of the carrier waves modulated by the signals P _i1 , P _i2 , ... P _iN on the light of these wavelengths λ _i (i = 1, 2, ..., M) are input to the M inputs of the multiplexer 316. Optical fiber (312, 313, 314, 315
etc.), are multiplexed by a multiplexer 316, and are finally output to one optical fiber 317. After long-distance multiplexed signal transmission is performed by the optical fiber 317, the light transmitted through the optical fiber 317 is first divided into M pieces by wavelength by a demultiplexer 318. The signals separated by wavelength are transmitted through M optical fibers (319, 3
20, 321, 322, etc.) and is input to M optical branchers (323, 324, 325, etc.) for each wavelength. Here, modulated waves ( _{i11 , i12} , _i13 , ...), ( _{i
twenty one} ,
_i22 , _i23 , ...), ( _iN1 , _iN2 , _iN3 , ...), the signal group P _i1 , P _i2 , ...P _iN is the same optical frequency filter circuit for any wavelength, regardless of the value of i. If the network group 330 can perform discrimination, M wavelength discrimination and N optical frequency filter network group 330 can perform discrimination. Note that the optical frequency filter network group 330 here includes N optical frequency filter circuit networks 32
It is assumed that this has been achieved from 9 onwards. Modulated wave ( _i11 ,
_i12 , _i13 ,…), ( _i21 , _i22 , _i23 ,…),
…( _iN1 ,
_iN2 , _iN3 , …) signal groups P _i1 , P _i2 ,
In order for P _i3 ,...P _iN to be discriminated by the same optical frequency filter network group 330 regardless of the value of i, _i11 = ₁ + S ₁₁ , _i12 = ₁ + S ₁₂ ,... < ₁ +△S _{1 1} +△S ₁ < ₂ −△S ₂ < _i21 = ₂ +S ₂₁ , _i22
= ₂ +S ₂₂ ,…< ₂ +△S _{2 2} +△S ₂ < ₃ −△S ₃ < _i31 = ₃ +S ₃₁ , _i32
= ₃ +S ₃₂ ,…< ₃ +△S ₃ ……… _N-1 +△S _N-1 < _N −△S _N < _iN1 = _N+ S _N1 ,
N optical frequency filter networks 329 may be designed as _iN2 = _N + S _N2 , . . . However, S ₁₁ , S ₁₂ ,…, S ₂₁ ,
S ₂₂ ,..., S _N1 , S _N2 ,... are sideband frequencies ₁ , ₂ ,
... _N is the frequency of the carrier wave, △S ₁ , △S ₂ ... are arbitrary frequencies that satisfy the above formula, and the sideband frequency and carrier wave frequency are determined so as to satisfy the above formula. Bandwidth (pass band) of N optical frequency filter networks BW ₁ ,
BW ₂ ,...BW _N are determined as follows.

BW ₁ < ₁ +△S _{1 2} −△S ₂ <BW ₂ < ₂ +△S _{2 3} −△S ₃ <BW ₃ < ₃ +△S ₃ …… _N −△S _N <BW _N carrier frequency> side If you choose the frequency of the wave band,
BW ₁ , BW ₂ ...BW _N can be selected narrowly enough.
In the case of intensity modulation, of course, BW ₁ , BW _{2 .} . . BW _N can be made sufficiently narrow by selecting carrier frequency≫sideband frequency. Also, in the case of frequency modulation, the modulation index is
It is known that if it is set to 0.5 or less, it is sufficient to consider two sidebands, upper and lower, and BW ₁ ,
BW ₂ ...BW _N can be made sufficiently narrow. Furthermore, when using the frequency displacement method, the required spectrum becomes narrower by decreasing the deviation ratio, so BW ₁ , BW ₂ ,...BW _N
can be narrowed. As described above, modulated waves ( _i11 , _i12 , ...), ( _i21 , _i22
，
…), ( _iN1 , _iN2 , …) signal group P _i1 carried by
，
The optical frequency filter network group 330 capable of discriminating P _i2 ...P _iN is divided into N optical frequency filter circuit networks 329.
It can be constructed from M optical splitters (323, 32
4, 325, etc.) are connected to M optical frequency filter network groups 330 via N optical fibers (326, 327, 328, etc.), respectively. The optical splitters (323, 324, 325, etc.) output signals separated by wavelength, and these signals are sent to the final destination via the optical frequency filter network group 330 designed as described above. is separated into MN signals and transmitted through optical fiber (3
32, 333, 334, etc.).

As is clear from the above description, the present invention, which uses wavelength multiplexing circuits and frequency multiplexing circuits using optical frequency filters in a composite manner, can achieve multiple wavelengths using just the wavelength multiplexing circuits.
If N multiplexing is possible with a frequency multiplexing circuit using an optical frequency filter, an MN multiplexing optical multiplexing circuit network can be constructed. Therefore, an optical multiplexing circuit that conventionally could perform multiplexing of only a few at most can be made into one that can perform multiplexing of at least ten or more. Therefore, the present invention has great benefits in the field of optical communications where high multiplexing is desired.

Furthermore, since the optical multiplex circuit has an all-optical configuration that uses no electricity at all except for the light emitting diode provided with the modulator, it is possible to realize an optical multiplex circuit with excellent explosion protection and noise resistance. Furthermore, although the light source itself used in the wavelength multiplexing circuit is expensive, by achieving high multiplexing of more than 10 wavelengths, the cost per line can be significantly reduced.

Fields of application of the present invention include multiplexing of public communication lines such as telephones using optical fibers, multiplexing of private communication lines using optical fibers of electric power companies, and plant measurement with strong requirements for explosion-proof performance. It can be applied to multiplex communication in measurement communication systems using optical fibers in the field.

[Brief explanation of drawings]

Figure 1 shows conventional wavelength multiplexing, Figure 2 shows an optical multiplexing circuit using an optical frequency filter, and Figures 3, 4, and 5 show the three basic configurations of optical frequency filters. Figure 6 is a diagram showing the characteristics of a feed-forward type optical frequency filter, Figure 7 is a diagram showing the characteristics of a feedback type optical frequency filter, and Figure 8 is a diagram showing the characteristics of a feed-forward operation hybrid type optical frequency filter. FIG. 9 is a diagram showing the characteristics of a feedback operation hybrid optical frequency filter, FIG. 10 is a diagram showing the function of the optical frequency filter, and FIG. 11 is a diagram showing the present invention. 1... Signal source with wavelength λ ₁ , 2... Signal source with wavelength λ ₂ , 3... Multiplexer, 4... Demultiplexer, 5, 6... Photoelectric converter, 7-11... Optical fiber , 108...
Light emitting element, 109, 111, 113, 114, 1
16... Optical fiber, 110... Brancher, 115
...Optical coupler, 112... Optical attenuator, 101...
Main path, 102... Bypass, 117... Light receiving element, 118... Optical frequency filter, 103...
...Main path, 104...Feedback loop, 105...Direct path, 106...Bypass, 107...Feedback loop, 119
... Splitter/Coupler, 120 ... Optical input, 1
21, 122... Optical fiber, 123... Optical output, 124, 125... Light intensity waveform versus time, 300, 301, 302... Signal input line, 303, 304, 305... Modulator, 30
6,307,308...Modulator output line, 30
9, 310, 311... Adder, 312, 31
3,314,315...optical fiber, 316...
Multiplexer, 317... Optical fiber, 318... Demultiplexer, 319, 320, 321, 322... Optical fiber, 323, 324, 325... Optical splitter, 3
26, 327, 328...optical fiber, 329...
Optical frequency filter network, 330... Optical frequency filter network group, 332, 333, 334... Optical fiber.

Claims (1)

[Claims] 1 An optical multiplexing circuit that transmits and receives multi-channel optical signals in an all-optical manner, which includes a plurality of first units each including a plurality of modulators and an optical coupler connected by an optical fiber; a plurality of second units in which a plurality of optical frequency filter circuit networks and an optical branching device are connected by an optical fiber; and a plurality of optical couplers provided in the plurality of first units are connected by an optical fiber one demultiplexer connected by an optical fiber to the plurality of optical splitters provided in the plurality of second units, and the one demultiplexer connected by an optical fiber. and an optical fiber connecting the plurality of first units and the one multiplexer, and the number of the plurality of first units is equal to the number of the plurality of second units, and the number of the plurality of first units is equal to the number of the plurality of second units, and the number of the plurality of first units is equal to the number of the plurality of second units. An optical multiplex circuit characterized in that the number of modulators included in each unit is equal to the number of optical frequency filter networks included in each corresponding one of the plurality of second units.