JPH09238123A - Optical communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable one photoelectric converter to receive signals from many terminal stations without deteriorating the quality of the signals. SOLUTION: Optical communication equipment modulates signals transmitted from terminal stations 11-1n into subcarrier signals having different frequencies and converts the subcarrier signals into intensity-modulated light by means of photoelectric converters 3 having different light emitting wavelengths and the intensity-modulated signals are received by means of the photoelectric converter 8 of a center station 7 through an optical fiber. The number (m) of simultaneously receivable waves of the converter 8 is smaller than the number (n) the intensity-modulated light rays. Each terminal station 1 has a pulsed light emitting function which emits intensity- modulated pulsed light modulated by a subcarrier signal for time division multiplexing having a frequency different from that of the above subcarrier signals by modulating the transmitted signals into the subcarrier signal for time division multiplexing in addition to a function which continuously emits the intensity-modulated light of the transmitted signals. The emission of the pulsed light is performed in accordance with the time slot of a time division multiplex system at every subcarrier signal for time division multiplexing and the photoelectric converter 8 always simultaneously receives intensity-modulated light equal to or less than the number (m) of simultaneously receivable waves.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optical CATV, an optical I.
Among optical communication devices such as TVs, optical transmission monitoring systems, and subscriber optical communication systems, a plurality of optical signals output from a plurality of points (terminal stations) are combined by one optical / electrical converter in the center station. The present invention relates to an optical communication device of a receiving form.

[0002]

2. Description of the Related Art There are various types of optical communication devices as described above, and one of them is shown in FIG. The optical communication device of FIG. 7 has terminal stations 1 ₁ , ... 1 at n different points.
_The central station 7 receives the transmitted signals such as _n video and audio in a centralized manner, and each of the terminal stations 1 ₁ , ...
1 The _n, the frequency f ₁ to be the transmission signal, the subcarrier signal sf ₁ ··· f _n, ··· sf _n modulator 2 ₁ for modulating the, and · · · 2 _n, the modulator 2 _1, sub-carrier signal sf ₁ output from · · · 2 _n, the · · · sf _n wavelengths λ
_1, the light intensity-modulated light Esuramuda ₁ · · · lambda _n, electrical / optical converter 3 ₁ for converting ··· sλ _n, is installed and · · · 3 _n, the one of the center station 7 , Light intensity modulated light sλ ₁ ,
... The optical / electrical converter 8 for receiving sλ _n , the distributor 10 for distributing the output signal of the converter 8, and the distributed sub-carrier signals sf ₁ , ... sf _n Demodulators 9 ₁ , ... 9 _n for demodulating the transmitted signal are installed. The subcarrier signals sf ₁ , ..., Sf
frequency f ₁ of _n, all different · · · f _n is also the light intensity-modulated light Esuramuda _1, wavelength lambda ₁ of ··· sλ _n, ··· λ _n are all different.

The modulators 2 ₁ , ... 2 _n are FM modulators and AM modulators for modulating analog signals, QPSK modulators and 64QAM modulators for modulating digital signals, etc. vessels 9 _1, · · · 9 _n the QP for demodulating FM demodulator and AM demodulator, a digital signal
It is an SK demodulator or a 64QAM demodulator. Further, the electric / optical converters 3 ₁ , ... 3 _n are usually DFB-LD, FP-
It is a light source such as an LD or an LED, or an optical transmitter in which these light sources are combined with an optical external modulator.

In the optical communication apparatus of FIG. 7, each terminal station 1 ₁ , ...
· Light intensity modulated light sλ ₁ , ... Sλ output from 1 _n
n are respectively propagated to the optical fibers 4 ₁ , ... 4 _n, and are multiplexed into one optical fiber 6 via the optical multiplexer 5 such as an optical star coupler. The plurality of light intensity modulated lights sλ ₁ , ..., sλ _n propagating through the optical fiber 6 are received by the optical / electrical converter 8 of the center station 7, and the original subcarrier signal sf is received by the optical / electrical converter 8. ₁ , ... Sf _n is reproduced. These subcarrier signals sf ₁ , ..., Sf _n pass through a distributor 10 and a demodulator 9
_1, is input to ... 9 _n, the demodulator 9 _1, ... 9
_{At n} , the original transmitted signals s1, ..., Sn are demodulated.

[0005]

In the optical communication system of FIG. 7 [0005] The subcarrier signal sf _1, ··· sf _n plurality of light intensity-modulated light modulated by Esuramuda1, the one ··· sλ _n light /
Although received together in electrical converter 8, in this case, the sub-carrier signal sf _1, ··· sf _n so that the transmission quality is not compromised in simultaneous receivable in the optical / electrical converter 8 wavenumber m There exists. However, the number m of waves that can be simultaneously received is all terminal stations 1 ₁ , ... 1 _n connected to the center station 7.
If the number is smaller than n, the center station 7 cannot receive signals from all the terminal stations 1 ₁ , ... 1 _n at the same time. The reason why the simultaneous receivable wave number m exists will be described below.

As one of the indexes of transmission quality when subcarrier signal transmission is performed, there is a ratio (C / N ratio) between the subcarrier signal power output from the optical / electrical converter 8 and the noise power. Particularly, when the multi-wave light intensity modulated light sλ ₁ , ..., sλ _n is received by one optical / electrical converter 8, the C / N ratio is shot noise determined by the characteristics of the optical / electrical converter 8. And thermal noise and beat noise generated at a frequency position corresponding to the wavelength difference of light. With respect to beat noise, the transmitted signal s1, whose effect is located at the carrier signal frequency, ...
.. to prevent sn from reaching each terminal ₁₁ .
・ Light wavelength λ ₁ of light intensity modulated light transmitted from 1 _n
・ Λ _n are set to different values with a certain interval. For example, if each station ₁ 1, · · · 1 _n of the electric / optical converter 3 _1, · · · 3 _n is DFB-LD is,
As shown in FIG. 8, the wavelength interval is usually set to 0.1 nm or more.

However, even when the influence of beat noise is suppressed to a minimum as described above, the C / N ratio usually deteriorates as the number of signal light waves increases, and simultaneous reception is possible while maintaining the transmission quality of each signal light. There is a wave number that can be received.
Therefore, in the optical communication device shown in FIG.
The number n of the terminal stations 1 ₁ , ... 1 _n connected to is larger than the maximum simultaneous received wave number m of the optical / electrical converter 8, that is, n> m.
If _n , only m stations in the _n terminal stations 1 ₁ , ... 1 _n are allowed to emit signal light, and the remaining n−m terminal stations stop emitting light from other stations. Unless done, no signal transmission is possible.

In order to solve such a problem, according to the present invention, in an optical communication device to which terminal stations whose number is larger than the maximum number m of simultaneously received waves of the optical / electrical converter 8 are connected, all the connected terminals are connected. An object is to realize an optical communication device that enables simultaneous reception from stations.

[0009]

Means for Solving the Problems An optical telecommunication system according to claim 1, wherein of the present invention as shown in FIGS. 1-3, the terminal station 1 _first plurality n, the transmission signal · · · 1 _n is respectively Modulated into subcarrier signals of different frequencies, these subcarrier signals are converted into light intensity modulated light by the electrical / optical converters 3 ₁ , ... 3 _{n having respectively} different emission wavelengths, and these light intensity modulated lights are converted into optical fibers. Light received by one of the optical / electrical converters 8 of the center station 7 via which the number m of simultaneously receivable waves of the optical intensity-modulated light in the optical / electrical converter 8 is smaller than the number n of all the optical intensity-modulated lights. In the communication device, each of the terminal stations 1 ₁ , ... 1 _n has a function of continuously emitting light intensity modulated light that is modulated by a subcarrier signal, and the transmitted signal has a frequency different from that of the subcarrier signal. This time-division multiplexing sub-carrier is modulated by the time-division multiplexing sub-carrier signal of It has a pulse emission function that emits a pulse of intensity-modulated light that has been modulated by an optical signal. This pulse emission is performed according to the time slot of the time division multiplex system set for each subcarrier signal for time division multiplex. The converter 8 always receives light intensity modulated light having a wave number m or less that can be simultaneously received.

An optical communication device according to a second aspect of the present invention has an electrical / optical converter 3 ₁ , ... 3 _n as shown in FIG.
However, the time-division multiplexing sub-carrier signal can be superimposed and transmitted on the light intensity modulated light that is modulated by the sub-carrier signal and continuously emitted, according to the time slot of the time-division multiplexing system of the signal.

An optical communication device according to a third aspect of the present invention, as shown in FIG. 6, has electrical / optical converters 3 ₁ , ... 3 _n.
However, the light intensity modulated light modulated by the subcarrier signal can also be pulse-emitted according to the time slot of the time division multiplex system.

In the optical communication device according to the fourth aspect of the present invention, the electric / optical converters 3 ₁ , ... 3 _n are DFB-LDs, and the electric / optical converters 3 ₁ ,. The light wavelength interval of the light intensity modulated light emitted from _n is 0.25 nm or more.

[0013]

First Embodiment A first embodiment of an optical communication device of the present invention will be described in detail with reference to FIG. N-number of the terminal station 1 ₁ in Figure 1, · · · 1 _n Each of the frequencies f ₁ to a target transmission signal respectively different input subcarrier signals · · · f _n s
f _1, modulator 2 ₁ for modulating the ··· sf _n, ··· 2 _n
, And the subcarrier signal f of the modulators 2 ₁ , ... 2 _n
1 , ... f _n with different emission wavelengths λ ₁ , ... λ _n
Of the light intensity-modulated light sλ _1, electrical modulating the ··· sλ _n /
The optical converters 3 ₁ , ... 3 _n are provided. Further, the sub-carrier signals sf ₁ , sf ₁ ,
... frequency f _{n +} 1, f _{n +} sub-carrier signal for time-division multiplexing of _{2 sf n + 1, sf n} + 2 modulator 2 _n + 1 for modulating the different from the sf _n, ... 2 _2n , _2n, and the electric / optical modulators 3 ₁ , ... _3n to control the modulator 2
_{n + 1,} sub-carrier signal for time division multiplexing is modulated by _{··· 2 2n sf n + 1,} sf n + 2 pulse emission of the light intensity modulated light sλ
_1, time division to ··· sλ _n multiplexing controller 11 _1, ·
.. 11 _n are provided.

The time division multiplexing subcarrier signal sf _{n + 1} ,
There are two waves of sf _{n + 2} in this example, and the terminal stations 1 ₁ , ...
· · 1 _i modulator 2 _{n + 1} of, ··· 2 n + _i first allocated time division multiplexing for sub-carrier signal sf n _{+ 1} when the relative end station 1
_{i + 1,} ... 1 _n modulator 2 _{n + 1} + 1 of have been assigned ... 2 sub-carrier signal for time-division multiplexing of the second relative _2n sf n _{+ 2.}

The center station 7 of FIG. 1 has one optical / electrical converter 8 and one distributor 10, and n + 2 demodulators 9 respectively.
₁ , ... 9 _{n + 2} . Demodulator 9 ₁ , ... 9
_n is for demodulating the received subcarrier signals sf ₁ , ..., sf _n , and the demodulators 9 _{n + 1} and 9 _{n + 2} are time-division multiplexing subcarrier signals sf _{n + 1} and sf _n. It is for demodulating ₊₂ . The demodulator _{9 n + 1, 9 n +} 2 , isolate time-division multiplexed signal demodulated by the demodulator _{9 n + 1, 9 n +} 2 terminal station 1 _1, the signal of each · · · 1 _n , A time division multiplexing controller 12 ₁ , 12 ₂ for reproducing the original transmitted signal
It has.

Next, an example of communication in the optical communication device of FIG. 1 will be described. Here, the optical / electrical converter 8 of the center station 7 has a wave number of m (m <n) that can be simultaneously received.
Of all the terminal stations 1 ₁ , ... 1 _n connected to, the m-2 station can output the light intensity modulated light sλ by continuous emission, and the remaining n- (m-2) stations emit light by pulsed emission. Intensity modulated light sλ
Can be output by time division multiplexing. Of the terminal stations 1 that emits pulsed light, the terminal stations 1 ₁ , ... 1 _i use the first subcarrier frequency f _{n + 1} for time division multiplexing, and the terminal stations 1 _{i + 1} ,.
.. 1 _n uses the second time division multiplexing subcarrier frequency f _{n + 2} .

In this case, as shown in FIG. 3, the terminal stations 1 ₁ , ...
· 1 each are _m-2, normal subcarrier frequency f _1, ...
Light intensity modulated light sλ ₁ by continuous emission using f _m-2 ,
... sλ _m-2 is output, and the terminal stations 1 _m-1 , ... 1 _i use the time division multiplexing subcarrier frequency f _{n + 1} to generate light intensity modulated light sλ _m-1 , ... sλ _i is output, and the terminal stations 1 _{i + 1} , ... 1 _n are time-division multiplexing subcarrier frequency f.
Light intensity modulated light sλ _{i + 1} by pulse emission using _{n + 2} ,
Outputs sλ _n . The light intensity modulated lights sλ _m-1 , ... sλ _i emitted from the terminal stations 1 _m-1 , ... 1 _i are set so as to follow the time-division-multiplexed time slot, and signals from each other may collide with each other. And the terminal station 1 _{i + 1} , ...
·· 1 _n emitted light intensity-modulated light sλ _i + 1, ··· sλ _n
Also follows the time-division multiplexing time slot, and signals do not collide with each other. In FIG. 3, the waveforms of the subcarrier signals sf carried on the light intensity modulated light sλ are all shown in the shape of a sine wave, but in reality, the shape depends on the time transition of the transmitted signal and the modulation method. different.

In this communication example, the optical signal from the center station 7 shown in FIG.
The electric intensity modulation light s of continuous light emission of m-2 waves is supplied to the electric converter 8.
λ and the light intensity modulated light sλ of the two-wave pulse light emission are received, and the m-wave signal light is always received. In other words, the number of signal lights exceeding the simultaneously receivable wave number m is not received, and the deterioration of the quality of signals multiplexed and transmitted is maintained.

[0019] Figure 2 is shows an example of an electrical signal output from the optical / electrical converter 8 of the central station 7 power (sub-carrier signal power) the horizontal axis the frequency, the frequency f _1,
· · · F _m-2 of the sub-carrier signal sf _1, the ··· sf _m-2 and an analog video signal is modulated, the frequency f
_{n + 1} , f _{n + 2} time division multiplexing subcarrier signals sf _{n + 1} , s
A digital signal is modulated on f _{n + 2} . This is because analog signals such as video signals having a very large amount of information can be transmitted by continuous light emission, and medium-narrow band data signals with a relatively small amount of information such as access signals and data signals can be transmitted by pulse light emission. This is because it is desirable from the viewpoint of efficient information transmission. As shown in the figure, the center station 7 receives the subcarrier signals sf ₁ , ..., Sfm _-2 which are constantly received by continuous light emission, and the subcarrier signals sf ₁ , ... Subcarrier signal s
f _{n + 1} and sf _{n + 2} appear.

In the above optical communication example, the terminal stations 1 ₁ , ... 1
_m-2 performs continuous light emission using the normal subcarrier frequencies f ₁ , ... F _m-2 , and the terminal stations 1 _m-1 , ... 1 _i perform time division multiplexing subcarrier frequency f _{n + 1.} , And the terminal stations 1 _{i + 1} , ..., 1 _n perform pulsed light emission using the time division multiplexing subcarrier frequency f _{n + 2} .
It is not limited to this setting. For example, a terminal station 1 that continuously emits light
Need not be m-2, and terminal station 1 that continuously emits light
May be replaced. The number of sub-carrier frequencies for time division multiplexing is not limited to two and may be one wave or three or more waves.

[0021]

Embodiment 2 It is also possible to perform a more advanced and practical communication mode by using the optical communication device of FIG. FIG.
Each end station ₁ 1, · · · 1 _n of the light-emitting functional of, in a state where the sub-carrier signal sf _1, are continuous emission send a · · · sf _n,
Subcarrier signal sf _{n + 1} or sf _{n + 2 of} time division multiplexing system
And when if it has a function that can be multiplexed in accordance with division multiplexing time slots, the terminal station 1 ₁ is performing a continuous emission transmission, can superimpose transmits the time division multiplexed signal also in · · · 1 _n, the optical communication device Improves flexibility.

FIG. 4 shows the electric / optical converter 3 ₁ , ... In this case.
.. This is a graph showing the time transition of the light emission power of 3 _n . As in the case of FIG. 3, terminal station ₁ 1, the · · · 1 _m-2, respectively frequencies f _1, · · · f subcarrier frequency sf ₁ of _m-2,
The signal light whose light intensity is modulated by sfm _-2 is continuously emitted. In addition to that, the subcarrier signal f _{n + 1} of the time division multiplexing system to which the own station belongs is also transmitted at a timing at which the own station is permitted to transmit. At this time, the terminal station 1 ₁ , ...
.. In 1 _m-2 , although the sub-carrier signal having a frequency of f _{n + 1} is transmitted in a pulsed manner, the light emission is continuous. Therefore, the optical / electrical converter 8 of the center station 7 still has the simultaneous received wave number. Is m
They are waves and the quality of the transmitted signal is not impaired.

[0023]

[Embodiment 3] As a more practical embodiment of the present invention, an electric / optical converter 3 _{1 of} each terminal 1 ₁ , ... 1 _n ,
・ ・ ・ Light intensity modulated light sλ ₁ emitted from 3 _n ,
The wavelengths λ ₁ , ... λ _n of sλ _n will be described. Terminal 1
_1, sub-carrier signal sf ₁ transmitted from · · · 1 _n, ·
Frequency f ₁ of ·· sf _n, ··· f _n is especially a few tens of MHz
The light sources used for the electrical / optical converters 3 ₁ , ... 3 _n of the terminal stations 1 ₁ , ... 1 _n are DFB-LDs. In this case, as described above, in order to avoid the influence of the beat noise generated in the optical / electrical converter 8, the wavelength interval of each signal light is usually set to 0.1 nm or more. This is because when the frequency of the sub-carrier signals sf ₁ , ..., Sf _n is several tens of MHz or more, the wavelength spectrum of the signal light extends over several GHz or more around the wavelength when light is emitted in the no-signal state. This is because it can be regarded as spreading. Therefore, in optical transmission using only continuous light emission, the wavelength interval of each signal light can be determined with reference to the wavelength when light is emitted in a non-signal state. However, in the case of performing pulsed light emission, light emission / stoppage is repeated, and the wavelength fluctuates during the light emission.

FIG. 5 shows the behavior of a general wavelength within the light emission time when light emission / stop is repeated. The emission wavelength λ0 when light is continuously emitted in a non-signal state is a low wavelength of about 0.1 to 0.15 nm immediately after the rising of light, and the behavior is such that it approaches λ0 with time. Therefore, in the present invention, the terminal stations 1 ₁ , ...
When the light source used for the 1 _n electro-optical converter 3 ₁ , ... 3 _n is a DFB-LD, the wavelength interval is set to 0.1 nm as in the conventional case, and light emission / stop is performed. While the above is repeated, the terminal station 1 that overlaps the wavelength of the adjacent light appears, and the quality of the transmission signal is impaired. In advance each terminal 1 ₁ ,
... By setting the wavelength interval of the signal light transmitted from the 1 _n electro-optical converter 3 ₁ , ... 3 _n to 0.25 nm or more, quality deterioration due to beat noise can be prevented in advance. Becomes

[0025]

Fourth Embodiment FIG. 6 shows an embodiment of a mode different from that of FIG. Here, in addition to the electric / optical converters 3 ₁ , ... 3 _n , each of the terminal stations 1 ₁ , ... 1 _n has two time division multiplexing control devices 11 (11 ₁ , ... 11 _2n). ) And a transmitted signal sent from the time division multiplex control device 11 as a subcarrier signal s having a frequency of f ₁ , f ₂ or f _3.
modulator 2 (2 for modulating to f ₁ , sf ₂ and sf ₃
1, ... 2 _2n ). In addition, the center station 7
In addition to the optical / electrical converter 8 and the distributor 10, the frequency is f
_1, f _2, subcarrier signal sf ₁ of f _3, sf _2, sf ₃
The demodulators 9 ₁ , 9 ₂ , 9 ₃ and the demodulated time-division multiplexed signal for demodulating the signals are separated for each terminal station 1 (1 ₁ , ... 1 _n ) to reproduce the original transmitted signal. The time-division multiplex control device 12 (12 ₁ , 12 ₂ , 12 ₃ ) is installed for this purpose.

In this system, three time division multiplex systems are set up, one of which belongs to the terminal stations 1 ₁ , ... 1 _i ,
The frequency of the subcarrier signal is f ₁ , the second belongs to the terminal stations 1 _{i + 1} , ... 1 _{n, and the} frequency of the subcarrier signal is f ₂ , and the third is the whole terminal. Station 1 ₁ , ...
1 _n belongs to the subcarrier signal frequency f ₃ .

In this system, the light of the center station 7 /
Consider a case where the number of simultaneously receivable waves in the electric converter 8 is 3 (3 <n). Terminals 1 ₁ , ... 1 _{n of} this system
3 time division multiplex systems are set for each terminal station 1
₁ ... 1 _n electric / optical converters 3 ₁ , ... 3 _n perform pulsed light emission at a timing at which the signal transmission of the local station is permitted according to the time slot of each time division multiplex system. Therefore, the optical / electrical converter 8 of the center station 7 receives a maximum of three waves of signal light, and the quality of the transmission signal does not deteriorate.

Also in this case, each terminal station 1 ₁ ,
_If the light source used for the 1 _n electric / optical converters 3 ₁ , ... 3 _n is a DFB-LD, the light is sent from each electric / optical converter 3 ₁ , ... 3 _n. If the wavelength intervals of the respective signal lights are set to be 0.25 nm or more apart from each other, the wavelengths are close to each other due to the wavelength fluctuation, and beat noise does not adversely affect the quality of the transmission signal.

Each of the optical communication devices of the present invention described above is not limited to the star type system configuration shown in FIGS. 1 and 6, but may be a bus type, a bus star type or the like for collecting signal light from multiple points. It can be applied to a communication device and can exert a sufficient effect also in these.

[0030]

The optical communication device of the present invention has the following effects. 1. Even if the number of simultaneously receivable waves at the center station is less than the number of all end stations connected to the center station, it becomes possible to receive signals from all end stations without exceeding the number of simultaneously receivable waves at the same time, and transmission. It is possible to receive without degrading the quality. 2. Since continuous light emission and pulsed light emission can be used separately, a signal with a large amount of information such as a video signal can be transmitted without difficulty, and the system has a wide application range and high flexibility. 3. The transmission capacity of the system can be utilized to the maximum and the system is highly efficient. Therefore, it is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an optical communication device of the present invention.

FIG. 2 is an explanatory diagram showing an example of a frequency spectrum of a subcarrier signal received by a center station.

FIG. 3 is an explanatory diagram showing a time transition of signal light power output from a terminal station.

FIG. 4 is an explanatory diagram showing a different example of the time transition of the signal light power output from the terminal station.

FIG. 5 is an explanatory diagram showing a state of wavelength variation when light emission / stop is repeated.

FIG. 6 is a schematic view showing another embodiment of the optical communication device of the present invention.

FIG. 7 is a schematic diagram showing an example of a conventional optical communication device.

8 is an explanatory diagram showing an example of a signal light array in the apparatus of FIG.

[Explanation of symbols] 1 terminal station 3 electric / optical converter 7 center station 8 optical / electrical converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Kubota 1-1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Inc. Incorporated (72) Inventor Shigeo Sudo 1-1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc.

Claims (4)

[Claims] 1. The transmitted signals of a plurality (n) of terminal stations (1 ₁ , ... 1 _n ) are modulated into sub-carrier signals of different frequencies, and these sub-carrier signals have different emission wavelengths of electric signals.
The optical converters (3 ₁ , ... 3 _n ) convert the light intensity modulated lights, and these optical intensity modulated lights are transmitted through an optical fiber to one optical / electrical converter (8) of the center station (7). Received,
In the optical communication device, the number of simultaneously receivable waves (m) of the light intensity modulated light in the optical / electrical converter (8) is smaller than the number (n) of all the light intensity modulated lights, the terminal stations (1 ₁ , ...・ ・ 1
_n ) has a function of continuously emitting light intensity modulated light that has been modulated by a subcarrier signal, and also modulates a transmitted signal into a time division multiplexing subcarrier signal of a frequency different from that of the subcarrier signal. Has a pulse emission function that emits a pulse of light intensity modulated light that has been modulated by a sub-carrier signal for time division multiplexing,
This pulse emission is performed according to the time slot of the time division multiplex system set for each time division multiplex subcarrier signal,
The optical / electrical converter (8) constantly receives light intensity modulated light having a wave number (m) or less capable of simultaneous light reception. 2. The electric / optical converter (3 ₁ , ... 3 _n )
The subcarrier signal for time division multiplexing can be superposed and transmitted on the light intensity modulated light which is modulated by the subcarrier signal and continuously emitted, according to the time slot of the time division multiplexing system of the signal. 1. The optical communication device according to 1. 3. The electro-optical converter (3 ₁ , ... 3 _n )
The optical communication device according to claim 1 or 2, wherein the optical intensity modulated light modulated by the subcarrier signal is also capable of emitting pulsed light in accordance with the time slot of the time division multiplexing system. 4. The electric / optical converter (3 ₁ , ... 3 _n )
Is a DFB-LD, the electric / optical converter (3 _1, ...
The optical communication device according to each of claims 1 to 3, wherein the light wavelength interval of the light intensity modulated light emitted from (3 _n ) is 0.25 nm or more.