JPS5966236A - Wavelength multiplex communicating method - Google Patents

Abstract

PURPOSE:To simplify the constitution of the titled wavelength multiplex device, by setting each of plural longitudinal mode wavelengths of a semiconductor laser as a channel wavelength to modulate the mode distribution form of the semiconductor laser. CONSTITUTION:The wavelengths lambday-1, lambday and lambday+1 of the longitudinal mode of a semiconductor laser 12' are set respectively as channels 1, 2, 3, and the channel to each wavelength is modulated with a digital time series signal of 0, 1 by a semiconductor laser modulating signal source 12 and the result is transmitted via an optical fiber 6. Thus, the semiconductor laser and its driving circuit which had been required for each channel, are one each, and since no wave synthesizer is required, the optical loss is reduced, simplifying remarkably the device.

Description

[Detailed Description of the Invention] Industrial Application Field' □ The present invention relates to a wavelength division multiplexing communication method using an angular semiconductor laser.

Conventional configurations and their problems In optical communications, wavelength division multiplexing can increase transmission capacity by using only one transmission path, and it also transmits different signals from the transmitting station to the receiving station. □It is a very effective □ method in some cases, and is currently being actively developed. □ An example of an optical communication method using semiconductor loops currently in practical use is shown in Figure 1. The semiconductor lasers □-the 1', 2' are modulated by the modulating signal sources 1, 2; 3, 4.

Since the oscillation wavelengths of A and 4' are all different, they have values. In other words, this optical communication device is an example of a four-wave multiplex system. The semiconductor laser beams are coupled to, for example, optical fibers 1', 2'', 3'', and 4', and are multiplexed by a multiplexer 6. The signal multiplexed by the multiplexer 6 is transmitted through a single transmission path, and at the receiving station, it is demultiplexed into light of different wavelengths by the demultiplexer γ, and the optical signal of each wavelength is sent to the detector 8.9.
, '10, 11, and the receiving circuit 8'',
The multiplexer 6 or demultiplexer 7, which detects the received signal at 9', 10', and 11', are optically equivalent products in terms of wood, but currently they are A method using a grid has been put into practical use.

As is clear from this wavelength multiplexed optical communication, if the modulation band of each semiconductor laser is determined, the total transmission capacity is determined by the number of integrated semiconductor lasers.

In addition, in the wavelength division multiplexing optical communication that is currently in practical use, the oscillation wavelength interval of semiconductor lasers is a matter of 100 to 2008 times. This is partly due to the insufficient wavelength dispersion ability of the wavelength demultiplexer and demultiplexer, but also because it is currently difficult to obtain multiple semiconductor lasers with a desired oscillation wavelength with high precision, in large quantities, and at low cost. In order to obtain such a semiconductor laser, semiconductor lasers whose wavelength can be precisely controlled, such as DFB lasers or DBR lasers, have been extensively researched.

However, (-1) Even if these semiconductor lasers with good wavelength controllability are used, one semiconductor laser is originally used as one channel of optical wavelength multiplexing communication, and the wavelength interval of each semiconductor laser is There is a limit to how accurate the settings can be.Furthermore, since the multiplexer 6 is an element whose purpose is to multiplex lights of different wavelengths from a plurality of semiconductor lasers, it is currently an indispensable component. The coupling loss caused by this cannot be ignored.

OBJECTS OF THE INVENTION The present invention eliminates all the drawbacks of the conventional technology and proposes a wavelength division multiplexing optical communication method from a new perspective.

In other words, instead of using one semiconductor laser as one channel of wavelength multiplexed communication as described in the conventional example, each longitudinal mode of several oscillation wavelengths of one semiconductor laser, that is, longitudinal multiple modes, can be The objective is to perform wavelength multiplexing communication using each wavelength as each transmission channel.

Structure of the Invention The wavelength multiplexing communication method of the present invention is characterized in that each of a plurality of longitudinal mode wavelengths of a semiconductor laser is used as a channel wavelength 2, and signal transmission is performed by modulating the mode distribution shape of the semiconductor laser. be.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described while comparing them with conventional ones. Second
Figure (a) shows the spectrum of a semiconductor laser used in a conventional wavelength division multiplexing communication method. That is, the lights emitted from different semiconductor lasers 1', 2', and 3' have different oscillation wavelengths λz-1, Ax, and Samurai+I. In this case, the oscillation wavelength λ, 2 knee, 1 t λ work, λ work and λL+1
The spacing is 100 to 208 people. FIG. 2(b) shows a transmitting station of a conventional wavelength division multiplexing communication device using three such imposter lasers.

3) shows the spectrum of the semiconductor laser used in the wavelength division multiplexing communication method of the present invention.

In the multiplex communication method according to this embodiment, each of the long waves of several longitudinal modes (three longitudinal modes in this embodiment) is transmitted from one semiconductor laser 12'! ,,,,.

λM, λy, -+ are respectively channel 1. Channel 2 and channel 3 will be used. A transmitting station using such a semiconductor laser is shown in Fig. 3 (b), but as is clear from a comparison with Fig. 2 (b), instead of three semiconductor lasers that were conventionally required, one semiconductor laser is required. All you need is a laser. Furthermore, the method of this embodiment eliminates the need for a multiplexer, which was necessary for multiplexing lights from different semiconductor lasers. Additionally, the spacing of each spectrum has become several times smaller.

For example, it is assumed that a digital modulated signal of 'Q1' is placed on a channel corresponding to each wavelength at a transmitting station as shown in FIGS. 2(b) and 3(b).

The time-series signal as shown in FIG. 4(l) is modulated at the transmitting station of FIG. 2(b) in the conventional example and FIG. 3(b) in the communication method according to the embodiment of the present invention. In the conventional communication method, this is achieved by turning on (ON) and turning off (OFF) the drive current to each '1' conductor laser.

On the other hand, in the communication method of the embodiment of the present invention, by allocating each longitudinal mode of one semiconductor laser to each channel, the oscillation group mode spectrum of the semiconductor laser is Signals are transmitted by changing from moment to moment. In other words, it is sufficient to be able to control the output vector of the semiconductor laser arbitrarily in terms of time, and this is possible by using a wavelength control type semiconductor laser, an external light feedback type semiconductor laser, or the like. Furthermore, assuming that the number of channels appropriate for one semiconductor laser, that is, the number of longitudinal modes, is 0, the total number of channels in the conventional wavelength division multiplexing communication method using m semiconductor lasers was m, but in the present invention, the total number of channels is m. P for the communication method of the example
In other words, if m semiconductor radars are used, the total number of channels will be (nxm), making it possible to extremely increase the transmission capacity.

Note that it is necessary to increase the wavelength dispersion ability of the splitter by making the channel wavelength spacing denser.

However, for example, the filter used in high-resolution spectrometers,
8□□5e6□n□77.4e. 4. A high-resolution duplexer used in the invention can be manufactured.

The young fruit of invention.

Comparing the wavelength division multiplexing communication method of the present invention with the conventional wavelength division multiplexing communication method, it is found that in the conventional wavelength division multiplexing communication method, m
However, in the present invention, n wavelengths can be controlled for oscillation. By using one semiconductor laser capable of Therefore, optical loss can be suppressed and the system itself can be simplified. f. If this system is applied to a conventional system with m semiconductor lasers, the number of transmission channels can be increased to (nxm), and the transmission capacity can be dramatically increased. walk

[Brief explanation of the drawing]

FIG. 1 is a diagram for decrystallizing a conventional fatigue-length multiplex, -wavelength signal, and FIG. 2 (4) is a diagram showing a signal channel and a wavelength spectrum in a conventional wavelength multiplex communication method. FIG. 2(b) is a diagram showing the configuration of a transmitting station in the same communication method; FIG.
Figure (b) is a diagram showing the configuration of a transmitting station in the same gate access method. FIG. 4(,,a) is a diagram showing time-series signals in the wavelength division multiplexing communication method of the conventional example and the embodiment of the present invention, and FIG. FIG. 3 is a diagram showing a laser oscillation spectrum. 1.2,3. M"Hln v -v'RmF@□9゜1
', 2', 3', 4'... Wave-heavy semiconductor laser, 1'', 2'''. 3'/, 4'... Optical fiber/f-bar, 6... Multiplexer, 6
... Optical fiber, 7... Brancher, 8, 9, 10.1
1...Detector. 8', 9', 10', 11'...receiving circuit, 12...
- Semiconductor laser modulation signal source, 12'...Wavelength controlled semiconductor laser O Name of agent: Patent attorney Toshio Nakao and one other person r-
'−−1″′−'−'−−'−−'−−−−'−−
−”−−−'−−11 H −−□Decoration□□□□□□□−轡1□□□th−2nd
Figure 4 (α)

Claims (1)

[Claims] A wavelength multiplexing communication method characterized in that each of a plurality of vertical mode wavelengths of a semiconductor laser is used as a channel wavelength, and signal transmission is carried out by modulating the longitudinal mode distribution shape of the semiconductor laser.