JPH0364136A - Bidirectional optical communication system - Google Patents

Abstract

PURPOSE:To easily and economically build up a 1:n communication system with excellent privacy call performance by assigning a specific wavelength respectively to the transmission line of an outgoing line to plural transmitter- receivers and providing a wavelength selectivity on an optical star coupler and branching the signal. CONSTITUTION:Optical signals whose wavelengths are different as lambda11-lambda1n from n (plural number) sets of transmitter-receivers 301-30n being transmission destinations are sent to an outgoing line from one station equipment 20 while being subject to time division control. On the other hand, a 1:n optical star coupler 50 has a function selecting and branching an optical signal of the outgoing line at every wavelength and optical signals of the wavelengths lambda11-lambda1n corresponding to the plural transmitter-receiver 301-30n are distributed. Thus, each of the transmitter-receivers 301-30n receives only an optical signal addressed to its own equipment respectively and the optical signals addressed to other equipments cannot be intercepted. Thus, the 1:n communication system with excellent privacy call performance is realized easily and economically.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a 1-to-n bidirectional optical communication system.

In particular, the present invention relates to a two-way optical communication system that ensures confidentiality of two-way optical communication.

[Prior Art] FIG. 8 is a block diagram showing a configuration example of a conventional 1:n two-way optical communication system.

In the figure, the transmitting/receiving end of one station device 80 and a plurality of n terminal devices 85 . An optical communication network consisting of optical fibers 91° to 7 and an optical star coupler 93 is set up between the transmitting and receiving ends of 851, and the downlink from the station equipment 80 has a wavelength of λ.
1. On the uplink, bidirectional optical communication is performed by wavelength multiplexing each optical signal of wavelength λ2.

The station device 80 includes a processing circuit 81 that performs signal transmission and reception processing;
A light source 82 that transmits an optical signal with a wavelength λ that is intensity-modulated according to the transmission signal information input from the processing circuit 81;
2, and a wavelength multiplexing circuit 84 that performs wavelength multiplexing and demultiplexing of the optical signals of wavelengths λ1 and λ2.

Each terminal device 85. -857 are processing circuits 861-7 that perform signal transmission and reception processing, light sources 871-fi that transmit optical signals with a wavelength λ2 whose intensity is modulated according to transmission signal information manually inputted from the processing circuits 861-7, and light sources 871-fi with a wavelength λ1. The optical signals are received and the received signal information is processed by the circuits 861 to . , a detection circuit 88. ~. , a wavelength multiplexing circuit 89 for wavelength multiplexing and demultiplexing optical signals of wavelengths λ and λ2. ~7.

The optical star coupler 93 is connected to the station equipment 80 for the downlink.
It has a function of branching an optical signal with a wavelength λ from 85 to 85 fi into a plurality of n signals, and a function of combining into one optical signal with a wavelength λ 2 from each terminal device 85° to 85 fi for the uplink.

Note that the identification of the optical signal corresponding to each terminal device is performed by the station device 80 and each terminal device 85 . - 85n, the position on the time axis assigned to each terminal device or the identification code added to the signal is detected.

[Problem to be solved by the invention]

By the way, such a conventional optical star coupler 93 connects each terminal device 85 . This configuration combines optical signals of wavelength λ2 from .
B) Since it is possible to do so, it is difficult for one terminal device to intercept the optical signal transmitted by the other terminal device,
Confidentiality is ensured.

However, the downlink optical signal (wavelength λ1
) are connected to each terminal device 851 through optical star coupler 93.
received by all 857. That is, each terminal device 8
5. ~85. Since each terminal device extracts a signal addressed to itself from among signals addressed to all terminal devices received at the same time, it is practically difficult to ensure confidentiality of communication.

An object of the present invention is to provide a two-way optical communication system that can easily realize two-way optical communication with excellent privacy.

[Means to solve the problem]

FIG. 1 is a block diagram showing the principle configuration of the system of the present invention.

The present invention provides a two-way optical communication system that performs two-way optical communication between opposing 1-to-n (n is an integer of 2 or more) transmitting and receiving devices via an optical communication network that includes an 1-to-n optical star coupler. In this case, one transmitting/receiving device includes a wavelength tunable light source capable of generating optical signals with a plurality of n wavelengths, and a wavelength control device that performs wavelength control corresponding to each of the plurality n transmitting/receiving devices facing the wavelength tunable light source. The 1:n optical star coupler selectively branches downlink optical signals of a plurality of n wavelengths transmitted from one transmitting/receiving device for each wavelength, and sends the optical signals to each of the plurality of n transmitting/receiving devices. The configuration is such that uplink optical signals of a predetermined wavelength transmitted from a plurality of n transmitting/receiving devices are combined into one and sent to one transmitting/receiving device.

[For production]

Optical signals with different wavelengths are time-division controlled and transmitted from one transmitting/receiving device (station device) to the downlink for each of a plurality of transmitting/receiving devices (terminal devices) that are transmission destinations. On the other hand, 1
The n-pair optical star coupler has a function of selectively branching downlink optical signals for each wavelength, and optical signals of corresponding wavelengths are distributed to each of the plurality of n transmitting/receiving devices. therefore,
Each of the plurality of transmitting/receiving devices receives only an optical signal addressed to itself, and cannot intercept optical signals addressed to other devices.

Further, on the uplink from a plurality of n transmitting/receiving devices, an optical signal of a predetermined wavelength is transmitted between one transmitting/receiving device under time division control between each transmitting/receiving device. On the other hand, a 1-to-n optical star coupler combines each optical signal on the uplink into one, but its directionality makes it easy to reduce mutual coupling, so that other transmitting/receiving devices can transmit it to the uplink. Optical signals cannot be intercepted.

In this way, in the downlink, by setting the wavelength for each transmitter/receiver and giving the 1:n optical star coupler wavelength selectivity, it is possible to easily maintain confidentiality in an I:N two-way optical communication system. can be secured.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing an embodiment of a 1:n bidirectional optical communication system according to the present invention.

In the figure, a transmitting/receiving end of one station device 20 and a plurality of n terminal devices 301 to 30. An optical communication network consisting of optical fibers 40° to 40n and a wavelength-selective optical star coupler 50 is set up between the transmitting and receiving ends of the station equipment 20, and the downlink from the station equipment 20 has wavelengths λII, λI , λ0, the uplink has a configuration in which bidirectional optical communication is performed by wavelength multiplexing each optical signal of wavelength λ2.

The station device 20 includes a processing circuit 21 that performs signal transmission and reception processing;
A wavelength tunable light source 22 transmits an intensity-modulated optical signal at a predetermined wavelength λ11 to λ1fi according to transmission signal information inputted from the processing circuit 21. a wavelength control circuit 23 that time-divisionally controls the corresponding wavelength settings; a detection circuit 24 that receives the optical signal of wavelength λ2 and outputs the received signal information to the processing circuit 21; It is composed of a wavelength multiplexing circuit 25 that performs wavelength multiplexing and demultiplexing of optical signals.

Each terminal device 301-30. Processing circuits 311 to . . . perform signal transmission and reception processing. ,, processing circuit 31. Light sources 321 to 7 transmit an optical signal of wavelength λ2 according to the transmission signal information manually inputted from ~7, and receive an optical signal of one wavelength of wavelength λ and ~λ11 assigned to each terminal device to generate a received signal. Information processing circuit 31. Detection circuit 33 that outputs to 7. ~
7. Wavelength λ4. The corresponding wavelength of ~λ1o and wavelength λ2
A wavelength multiplexing circuit 34+ that performs wavelength multiplexing and demultiplexing of each optical signal of
-9.

The wavelength selective optical star coupler 50 receives wavelengths λ1... from the station equipment 20 for the downlink. A function of selectively branching optical signals of .about.λ17 to optical fibers 401 to 40n corresponding to each terminal device, and a function of selectively branching optical signals of λ17 to each terminal device 30.about.17 for uplink. ~30
It has a function of combining optical signals of wavelength λ2 from n into one.

FIG. 3 is a diagram showing an example of wavelength allocation of optical signals transmitted bidirectionally in the configuration of the embodiment.

In the figure, the wavelength λ2 of the uplink optical signal is, for example, 1
．． It is arranged in the 3 μm band (1300 nm). In addition,
In that case, each terminal device 301-30. light source 321
~． The wavelengths of can be set to exactly the same wavelength, or
Or within a predetermined range in the 1.3 μm band (for example, 1300
nm to 1320 nm) may be different. Note that the predetermined range is set depending on the characteristics of the wavelength selective optical star coupler 50 and the detection circuit 24 of the station device 20.

Furthermore, the wavelengths λ11 to λ of the downlink optical signals are arranged, for example, in the 1.5 μm band (1500 nm). Note that the wavelengths λ, to λIn are within the wavelength tunable range of the wavelength tunable light source 22, and normally λ8. -λI, ll: several nm. Therefore, each wavelength λ11, λ1□1,
... are, for example, 1500n m and 1501n, respectively.
m, -. Note that such a wavelength tunable light source 22
For example, a well-known distributed feedback (DFB) semiconductor laser or distributed plug reflection (DBR) semiconductor laser is used. In such a semiconductor laser, the intensity of output light is controlled according to the injection current applied to its intensity control electrode (transmission signal information from the processing circuit 21), and the intensity of the output light is controlled according to the injection current applied to its wavelength control electrode (wavelength This is a configuration in which the wavelength of output light is controlled according to wavelength control information (from the control circuit 23).

The station device 20 time-divisionally transmits optical signals with different wavelengths for each destination terminal device based on the wavelength arrangement example shown in FIG.

FIG. 4 is a time chart of optical signals transmitted on the downlink of optical fibers 40° to 40,1.

FIG. 4(a) shows light emitted from the station equipment 2o and transmitted through the optical fiber 40. shows an optical signal input to the wavelength-selective optical star coupler 50 via the wavelength-selective optical star coupler 50.
7 burst signals are transmitted sequentially. Each burst signal is a pulse signal that is intensity modulated at a corresponding wavelength according to a predetermined modulation code.

FIG. 4(b) shows an optical signal emitted from the wavelength-selective optical star coupler 50, which is selected for each wavelength and connected to the optical fiber 40. It is branched to 407. Therefore, in each terminal device 301-301°, the corresponding optical fiber 40. ~40,1, only burst signals addressed to the terminal device are received, and burst signals addressed to other terminal devices cannot be received, so that confidentiality can be ensured.

FIG. 5 shows an optical fiber 40. 2 is a time chart of optical signals transmitted on the uplink.

The wavelength-selective optical star coupler 50 selects the uplink wavelength λ2.
There is no wavelength selectivity for optical signals.

Therefore, each terminal device 30. ~30. Optical signals of wavelength λ2 transmitted in a time-divisional manner according to predetermined communication rules are combined by a wavelength-selective optical star coupler 50 and transmitted to the station equipment 20 via an optical fiber 40°. Station device 20
In this system, a code identifying a transmitting terminal device is detected from each burst signal and reception processing is performed.

Note that each terminal device 30. ~30. Due to the directionality of the wavelength-selective optical star coupler 50, the optical signals transmitted from the
B) Since it is possible to do so, it is difficult for one terminal device to intercept the optical signal transmitted by the other terminal device,
Confidentiality is ensured.

Further, in the uplink shown in FIG. 5, a guard time G is set so that the burst signals do not overlap, but a guard time may be set in the same way in the downlink. This guard time in the downlink is effective when the signal speed is particularly high and the transition time required for wavelength switching of the wavelength tunable light source 22 cannot be ignored.

FIG. 6 is a flowchart illustrating the operation of the wavelength control circuit 23 of the station device 20. Note that the wavelength control circuit 23 includes a microprocessor that processes transmission destination information from the processing circuit 21 and a DC current generation circuit that generates a corresponding control current. Further, FIG. 6(a) shows the case of synchronous transfer mode, and FIG. 6(b) shows the case of asynchronous transfer mode.

In FIG. 6(a), a control signal for starting transmission is input from the processing circuit 21, and "1" is set in the counter.

Injection current ■=1 (N) is set according to the value N of the counter, and is applied to the wavelength control electrode of the wavelength tunable light source 22.

Note that the injection current 1 (N) according to the counter value N is:
The correspondence relationship between a predetermined time position and a destination terminal device is determined in advance, and is set by referring to it (STM
mode).

When the application time of the injection current I = I (N) exceeds a predetermined time, the counter is incremented, and the injection current is sequentially updated until the counter value N exceeds the number n of terminal devices, and the optical signal of the corresponding wavelength is is transmitted in a time-division manner. Furthermore, when the counter value N exceeds the number n of terminal devices, the counter is reset and the same process is repeated.

In FIG. 6(b), the destination terminal device is determined from the transmission destination information (encoded label) inputted from the processing circuit 21. Subsequently, the injection current (2) is set according to the wavelength corresponding to the destination terminal device, and is applied to the wavelength control electrode of the wavelength tunable light source 22.

FIG. 7 shows a wavelength-selective optical fiber used in the method of the present invention.
It is a diagram showing the configuration of an embodiment of the cover.

Here, the configuration of a basic unit that performs one-to-two branching and coupling is shown.

In the figure, the basic units are an interference filter 75 connected to an input/output port 71 via an optical waveguide 73, and a Mach-Zehnder interferometer 85 connected to an input/output port 77.79 via an optical waveguide 81.83. , and two optical waveguides 87 and 89 connecting the interference filter 75 and the human output section of the Mach-Zehnder interferometer 85.

The Mach-Zehnder interferometer 85 is connected to the directional coupler 9 connected to the input/output boat 77, 79 via the optical waveguide 81183.
1, a directional coupler 93 connected to the interference filter 75 via an optical waveguide 87, 89, and each directional coupler 91.
93 and two optical waveguides 95 and 97. In the Maha-Zehnder interferometer 85, a predetermined wavelength selectivity is achieved by appropriately setting the optical path length difference between the two optical waveguides 95.97 that connect the directional couplers 91.93.

Further, the interference filter 75 is configured to totally reflect the wavelength island and the optical signal of λ1□, and have a 50% transmission characteristic for the optical signal of wavelength λ2.

Here, the wavelength λ, (e.g. 1500 nm) and λ1
□ (for example, 1501 nm) optical signal is input to/output port 7.
It is assumed that an optical signal of wavelength λ2 (for example, 1300 nm) is input from human output ports 77 and 79, respectively.

The wavelength C incident from the input/output boat 71 and λ,2
The optical signal is totally reflected by the interference filter 75 and passes through the optical waveguide 8.
7 and enters the Mach-Zender interferometer 85. The Mach-Zehnder interferometer 85 separates optical signals of wavelengths λ11 and λ1□ according to predetermined wavelength selectivity, and outputs them from input/output boats 77 and 79, respectively.

Further, the optical signal of wavelength λ2 inputted from the input/output boat 77 is transmitted to the optical waveguide 87.
The light is emitted to both or one of 89. That is,
Since the Mach-Zehnder interferometer 85 has wavelength selection characteristics set for optical signals of wavelengths λ and λ12, the output light for wavelength λ2 differs depending on the value.

In any case, the optical signals that have passed through both or one of the optical waveguides 87 and 89 are combined by the interference filter 75 and output from the input/output boat 71. Note that in an ideal case where there is no coupling loss in the interference filter 75, the optical signal of wavelength λ2 has a light intensity (%) of the light intensity incident on the input/output boat 77.
3dB) and is emitted from the human output port 71.

Similarly, the optical signal of wavelength λ2 inputted from the input/output boat 79 is outputted from the human output boat 71.

Note that the wavelengths of the optical signals input from the human power boats 77 and 79 do not necessarily have to be the same wavelength λ2, but can be different wavelengths as long as the wavelength band corresponds to the 50% transmission characteristic of the interference filter 75. The same operation is possible for

Further, the 1:4 wavelength selective optical star coupler is realized by configuring the basic units shown above in two stages.

That is, in the basic unit of the first stage, optical signals with wavelengths λ11 and λ12 and optical signals with wavelengths λ, 3, λ, and 4 are branched, and in each basic unit of the next stage, optical signals of each wavelength are branched. The configuration is such that an optical signal of wavelength λ2 is sequentially coupled to one input/output port in the basic unit of each stage.

The same is generally true for 1:n wavelength selective optical star couplers.

[Effects of the Invention] As described above, the present invention has a configuration in which a unique wavelength is assigned to each downlink transmission signal to a plurality of n transmitting/receiving devices, and the optical star coupler is branched with wavelength selectivity. A one-to-n two-way optical communication system with excellent privacy can be constructed economically and easily.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle configuration of the present invention. FIG. 2 is a block diagram showing an embodiment of a 1:n bidirectional optical communication system according to the present invention. FIG. 3 is a diagram showing an example of wavelength allocation of optical signals transmitted bidirectionally in the embodiment configuration. FIG. 4 is a time chart of optical signals transmitted on the downlink. FIG. 5 is a time chart of optical signals transmitted on the uplink. FIG. 6 is a flowchart explaining the operation of the wavelength control circuit of the station equipment. FIG. 7 is a diagram showing an embodiment of the configuration of a wavelength-selective optical star coupler used in the system of the present invention. FIG. 8 is a block diagram showing a configuration example of a conventional l-to-n two-way optical communication system. 20... Station device, 21... Processing circuit, 22... Tunable wavelength light source, 23... Wavelength control circuit, 24... Detection circuit, 25... Wavelength multiplexing circuit, 30... Terminal device, 31... Processing circuit, 32... Light source, 33... Detection circuit, 34... Wavelength multiplexing circuit, 40... Optical fiber, 50... Wavelength selective optical star coupler, 71.7
7.79...I/O boat, 73.81.83.87
．． 89.95.97... Optical waveguide, 75... Interference filter, 85... Mach-Zehnder interferometer, 91.93.
...Directional coupler. Figure 3 (a) (11)) Figure 3 (a) (b) Figure 3

Claims (1)

[Claims] (1) In a two-way optical communication system that performs two-way optical communication between opposing 1-to-n (n is an integer of 2 or more) transmitting and receiving devices via an optical communication network that includes a 1-to-n optical star coupler. , One transmitting/receiving device includes a wavelength tunable light source capable of generating optical signals with a plurality of n wavelengths, and a wavelength control device that performs wavelength control corresponding to each of the plurality n transmitting/receiving devices facing the wavelength tunable light source. The 1-to-n optical star coupler selectively branches downlink optical signals of a plurality of n wavelengths transmitted from one transmitting/receiving device for each wavelength, and transmits the optical signals to each of the plurality of n transmitting/receiving devices, respectively. A two-way optical communication system characterized in that optical signals of a predetermined wavelength on uplinks transmitted from a plurality of n transmitting/receiving devices are combined into one and sent to one transmitting/receiving device.