JPH0653936A - Optical signal time-division multiplex transmitting method - Google Patents

Abstract

PURPOSE:To increase a transmission capacity by improving the transmitting speed of the time-division multiple transmission of an optical signal by using an optical device instead of an electronic circuit such as a multiplexer circuit. CONSTITUTION:Electric signals f(1)-f(n) of (n) channels are simultaneously inputted to an electric/optic conversion circuit 11 in parallel. The converted optical signals of the (n) channels are simultaneously inputted in parallel to (n) pieces of optical delay line group 12 whose delay amounts are successively different in each reference delay time corresponding to the time width of the time slot of each channel in a time-division multiple, and a synthesizer 13 which synthesizes the output optical signal of each delay line. Then, a time-division optical signal constituted of the optical signals of the (n) channels successively delayed in each reference delay time is taken out as the synthesized output, and transmitted to a single optical transmission line 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal time division in which optical signals of a plurality of channels are sequentially and repeatedly switched for each time slot of a reference time width and are transmitted by a single optical transmission line in the form of a time series optical signal. More specifically, the present invention relates to a multiplex transmission method, in which the reference time width of a time slot in time division multiplexing is made extremely short as compared with the conventional one so as to remarkably increase the transmission capacity.

[0002]

2. Description of the Related Art As one method for increasing the transmission capacity of optical signals in optical communication, there is a time division multiplex transmission system in which optical signals of a plurality of channels are sequentially converted into alternating cyclic time series optical signals and transmitted as described above. However, a conventional optical signal transmission system based on this type of transmission system is configured using a multiplexer circuit represented by a rotation changeover switch as shown in FIG.

In the conventional optical signal time division multiplex transmission system having the configuration of FIG. 1, simultaneously generated n-channel electrical signals f (1) to f (n) are temporarily stored in the input buffer memory 1 and a clock signal is generated. Under control of the multiplexer circuit 2, the electrical signals f (1) to f (n) read out by sequentially switching by a predetermined time slot time width by the multiplexer circuit 2 are converted into electrical signals by the drive circuit 3a and the optical signal modulator 3b. The optical conversion circuit 3 converts it into a time-series optical signal and sends it to the optical transmission line 4.

Then, the time-series optical signals from the optical transmission line 4 are divided into optical demultiplexing circuits 5a and n photodetectors 5b in parallel.
₁ ～5B by _n and the amplifier 5c ₁ ~5c _n optoelectronic converter 5 made by inverse transform in time series electric signals in parallel and supplied in parallel to respective input terminals of a multiplexer circuit 6 (1) ~ (n) , N-channel electric signals f (1) to f (f) taken out by sequentially switching the time-series electric signals by a predetermined time slot time width while synchronizing with the multiplexer circuit 2 on the transmission side under the control of the clock signal. (n) is sequentially supplied to the output buffer memory 7 and distributed to each memory address and stored.

In the above-mentioned conventional optical signal time division multiplex transmission system, in order to increase the transmission capacity, a buffer memory 1 is arranged at the input end, and electric signals of a plurality of channels are temporarily stored in the buffer memory 1. Then, the multiplexer circuit 2 sequentially switches the electrical signals of a plurality of channels stored in the buffer memory 1 in parallel at the same time to convert the electrical signals into time series signals, and at the same time, performs electrical / optical conversion and reconverts them into time series optical signals. There is.

[0006]

Generally, in an optical signal transmission system, in order to convert an electric signal obtained as information into an optical signal for transmission, the electric device and the optical device are used together as described above. It is always. However, the operating speed of the electric device is slower than that of the optical device, which significantly suppresses the transmission speed of the entire optical signal transmission system. Even in the above-mentioned conventional optical signal time division multiplex transmission system, the channel switching speed of the multiplexer circuit uniquely determines the transmission amount of the transmission system, that is, the number of signal channels of parallel simultaneous occurrence which can be transmitted in the form of time series signals. However, the transmission capacity is limited by the channel switching operation speed of the multiplexer circuit.

[0007]

As means for increasing the transmission capacity of time division multiplex transmission, that is, the switching speed of multiple channels, in addition to speeding up the operation of electrical or electronic devices such as multiplexer circuits, It is conceivable to increase the multi-channel switching speed by using a new method.

The object of the present invention is to solve the problems by eliminating the above-mentioned drawbacks of the conventional system, and to prevent the above problems from occurring in electronic circuits which are obstacles to the speed-up of optical signal time division multiplex transmission, such as the above-mentioned input buffer. An object of the present invention is to provide a new optical signal time division multiplex transmission system that configures a time division multiplex transmission system by using an optical device, in particular, an optical delay line such as an optical fiber, instead of a memory or a multiplexer circuit.

That is, the optical signal time division multiplex transmission method of the present invention is a conventional optical signal time division multiplex transmission system in which optical signals of a plurality of channels are sequentially and repeatedly switched at predetermined time lengths and transmitted by a single optical transmission line. In comparison with the above, in the optical transmission, the optical signals of a plurality of channels are simultaneously input in parallel to each of the plurality of optical delay lines having different lengths as the reference predetermined time length unit, and the plurality of optical delay lines are simultaneously input in parallel. The output optical signals sequentially delayed by a predetermined time length of the two optical delay lines are sequentially supplied to the single optical transmission line, and the optical signals of the simultaneous parallel channels are transmitted in the form of time-series optical signals. It is characterized by doing so.

[0010]

Therefore, in the optical signal time division multiplex transmission system of the present invention, the operating speed of the electronic circuit for time division multiplexing such as the multiplexer circuit which has been an obstacle to the increase of the transmission rate of this kind is restricted. In addition, the transmission speed of the time division multiplex transmission of the optical signal can be remarkably improved, and thus the transmission capacity can be dramatically increased.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 shows an example of the configuration of an optical signal time division multiplexing transmission system according to the method of the present invention. In the configuration example shown,
The n-channel electrical signals f (1) to f (n) are n in parallel, and the amplifiers 11a-1 to 11a-n and the optical signal modulator 11b- are arranged in parallel.
1 to 11b-n are simultaneously input to the electrical / optical conversion circuit 11 in parallel, and the electrical signal f (1) is supplied under the control of the clock signal.
The optical signals of n channels obtained by converting f to f (n) are sequentially changed by the reference delay time corresponding to the time width of the time slot of each channel in the time division multiplexing, and n optical delay line groups 12 and The output signals of the respective optical delay lines are simultaneously input to the multiplexer 13 in parallel, and the time-series optical signal composed of the n-channel optical signals sequentially delayed by the reference delay time is taken out as the multiplexing output. The time-series optical signal formed without depending on the switching operation like the method is sent to the single optical transmission line 4. Therefore, under the control of the clock signal, the n-channel electrical signals that are input to the electrical / optical conversion circuit 11 in parallel at the same time are switched between the n-channels for each period corresponding to the time slot time width of time division multiplexing. If the signals are sequentially input in a cycle, the time-series optical signal formed without being restricted by the operation speed of the electric device or the electronic device as in the conventional system can transmit the transmission capacity or the transmission channel of the optical signal to be time-division multiplexed. The number can be increased dramatically.

The time-division multiplex system based on the sequential delay time difference does not use any electrical or electronic circuit for forming the time-series signal, and therefore, compared with the conventional time-division multiplex system using the multiplexer circuit, It is possible to adopt an ideal configuration in which the dynamic multiplicity depends only on the operating speed of the light source drive circuit on the transmission side. That is, while the time required for channel switching by the conventional multiplexer circuit is on the order of several hundred nanoseconds to several microseconds, the above-mentioned light source drive circuit is currently capable of high-speed operation of 10 GHz to 20 GHz, and time division multiplexing. The temporal multiplicity in the transmission increases significantly.

The principle of the optical signal time division multiplex transmission system according to the method of the present invention-In the configuration shown in FIG. 2, the time-sequential optical signals from the optical transmission line 4 are demultiplexed to obtain parallel and simultaneous n-channel signals. Also in the case of restoration, the demultiplexer 15 and the optical delay line group 16 having the same configuration as that used for forming the time-series optical signal described above are used to correspond to the time width of the time slot of each channel in time division multiplexing. The optical transmission line 4 is connected to the n optical delay line groups 16 whose delay amounts are sequentially different for each reference delay time.
Input the time series optical signals from the
Each of the output optical signals of 6 is a photodetector 17a-1 of n in parallel.
.About.17a-n and amplifiers 17b-1 to 17b-n, the n-channel electrical signal inversely converted by the optical / electrical conversion circuit 17 is converted into a time-division multiplexed time slot time width under the control of the clock signal. Only in a corresponding period, in synchronization with the electric-optical conversion circuit 11 on the transmission side, the n-channel electric signals f (1) to f (f) which are sequentially taken out and restored in parallel in a cycle in which n-channel switching makes one cycle are restored. n) are simultaneously output in parallel via an electric shift register or the like to an output buffer memory array 18
Sequentially store in each memory address of. Further, when an optical memory such as a photon / echo memory is put to practical use in the future, a system configuration as shown in FIG. 3 can be considered.

Therefore, the formation of the time division multiplexed time series optical signal and the decomposition of the time series optical signal in the configuration example shown in FIG. 2 all depend only on the difference in the optical signal transmission delay amount between the respective channels. Therefore, regardless of the frequency or the wavelength of the n-channel carrier optical signal, they can all have the same frequency or the same wavelength.

On the other hand, when the frequencies or wavelengths of the n-channel carrier optical signals are different from each other, the optical signal time division multiplexing transmission system according to the method of the present invention is constructed as shown in the example of FIG. In place of the optical delay line group 16 on the input side, n optical filter groups 19 each having a pass band corresponding to the frequency or wavelength of the n-channel carrier optical signal on the input side in a one-to-one manner are used. The multiplexed time-series optical signals that are simultaneously input in parallel through the demultiplexer from 4 are discriminated in frequency or wavelength for each channel and are supplied to the corresponding optical / electrical conversion circuits. After that, the signals are sequentially (or simultaneously) stored in the buffer memory 18 under the synchronous control by the start clock signal or the like from the transmitting side.

Further, as shown in FIG. 5, the configuration example shown in FIG. 2 and the configuration example shown in FIG. 4 are combined to remarkably increase the degree of multiplexing of information in the optical signal time division multiplex transmission of the method of the present invention. You can also That is, the simultaneous electrical signals f
(1) to f (n) are converted into different n-channel modulated light,
Furthermore, when there are m transmission channels of n channels (that is, when the channel has a multiplicity of m channels), information signals of m × n channels are multiplexed by time division and transmitted, and extremely high speed and large capacity information is transmitted. Transmission can be achieved.
As shown in FIG. 5, this is a major feature that the system can be constructed very easily by adding one stage of multiplexer on the signal transmitting side and the receiver can be reduced to 1 / m.

Next, FIG. 6 shows an example of the detailed construction of the fitting portions of the optical delay line group 12 and the multiplexer 13 used in the optical signal time division multiplexing transmission system of the method of the present invention, and the concrete construction of each portion. An example of is shown in FIG. That is, in order to form a time-series optical signal by the optical signal time division multiplexing of the method of the present invention, the n-channel carrier optical signal modulated by the n-channel information signal is simultaneously paralleled and the optical modulators 11b-1 to 11b-. The signal is supplied to the optical delay line 12 including n optical fibers or the like inserted between n and each input terminal of the multiplexer 13. The length L of each optical delay line 12 differs from the minimum length L _{0 in} order of the basic delay time Δt corresponding to the time width of the time division time slot as a unit, Δt to (n−1). Let Δt be the length obtained by sequentially adding. When the refractive index of the optical fiber is N, the delay time of each optical delay line is given by 1 / N. In addition, both ends of the optical fiber constituting each optical delay line 12c are tapered so that they are fitted into the guide pin holes shown in FIG. 7 (b) of the fiber fitting device 12a, and at the same time the V groove base 12b is fitted. The optical transmission loss in the optical coupling part is reduced by placing it in the V groove 12d shown in FIG. 7 (a).
It is necessary to devise a mechanically simple structure.

[0018]

As is apparent from the above description, according to the present invention, in the optical signal time division multiplex transmission method, the multiplexer circuit etc. which has been an obstacle to increase the transmission rate in the related art,
The transmission speed of optical signal time division multiplex transmission is remarkably improved without being restricted by the operation speed of the electronic circuit for time division multiplexing. Therefore, the transmission capacity, that is, the information signal multiplicity is dramatically improved as compared with the conventional one. It is possible to bring about a particularly remarkable effect of increasing it.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a conventional optical signal time division multiplexing transmission system.

FIG. 2 is a block diagram showing a configuration example of an optical signal time division multiplexing transmission system of the present invention.

FIG. 3 is a diagram showing an example using an optical memory in the optical signal time division multiplex transmission system of the present invention.

FIG. 4 is a block diagram showing a configuration example of modulated light (wavelength, frequency, or the like) with all different inputs in the optical signal time division multiplexing transmission system of the present invention.

FIG. 5 is a diagram showing a configuration in a case where an optical signal of an input stage has an n-th degree of multiplicity and an input block has an m-th degree of multiplicity.

FIG. 6 is a diagram showing a detailed configuration example of an optical delay line group used in the optical signal time division multiplexing transmission system of the present invention.

FIG. 7 (a) is a cross-sectional view schematically showing a configuration example of a V-groove base used for the same optical delay line group, and FIG. 7 (b) is a configuration of a fiber fitting device also used for the same optical delay line group. It is sectional drawing which shows an example typically.

[Explanation of symbols]

 1,7 Buffer memory 2,6 Multiplexer circuit 3,11 Electric / optical conversion circuit 3a, 5c, 11a, 17b Amplifier 3b, 11b Optical modulator 4 Optical transmission line 5,17 Optical / electrical conversion circuit 5a, 15 Demultiplexer 5b, 17a, 27 Optical detector 12, 16 Optical delay line group 13 Multiplexer 18 Buffer memory array 19 Optical filter group 20 Header translator 21 Sequence controller 22 Electrical shift register 23 Clock signal 24 Output terminal 25 O / E conversion circuit 26 Two-dimensional optical memory array

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04J 3/00 Q 8843-5K

Claims (3)

[Claims] 1. An optical signal time-division multiplex transmission method in which optical signals of a plurality of channels are sequentially and repeatedly switched at predetermined time lengths and transmitted by a single optical transmission line, and a predetermined length that requires the predetermined time length for optical transmission. Optical signals of a plurality of channels are simultaneously input in parallel to a plurality of optical delay lines having different lengths, respectively, and are sequentially delayed by a predetermined time length of the plurality of optical delay lines. Optical signal time division multiplexing, characterized in that each output optical signal is sequentially supplied to the single optical transmission line, and simultaneous parallel optical signals of a plurality of channels are transmitted in the form of a time-series optical signal. Transmission method. 2. The time-series optical signals transmitted by the single optical transmission line are input in parallel to a plurality of optical delay lines on the other receiving side, each of which has a different length by a predetermined length, and the time-series optical signals are input in parallel. Each output optical signal of another optical delay line is taken out in parallel at the same time corresponding to the simultaneous parallel input of the optical signals of a plurality of channels to a plurality of optical delay lines for a period of a predetermined time length in each cycle of the repetition. The optical signal time division multiplex transmission method according to claim 1, characterized in that. 3. An optical signal such as wavelength-multiplexed or frequency-multiplexed optical signal in which optical signals of a plurality of channels are multiplexed with optical signals of a plurality of wavelengths or a plurality of frequencies whose modulated lights by wavelengths or frequencies are different for each channel. The optical signal time division multiplexing transmission method according to claim 1 or 2, characterized in that.