JPS636993A - Wavelength division type optical exchange system - Google Patents

Abstract

PURPOSE:To increase the number of input lines (output lines) while maintaining a low loss in an insertion and a satisfactory crosstalk characteristic by selecting and dividing an optical wavelength by the use of a wavelength variable laser diode to perform an optical exchange. CONSTITUTION:Optical signals of the different wavelength lambda1, lambda2,... are transmitted through an optical fiber from plural (n) terminals, the (n) pieces of optical signals are inputted to n X n port type optical star couplers 9 having (n) input and output ports, output light from the output port is inputted to the wavelength variable laser diode 10, and the output light from the respective laser diodes is transmitted to respective terminals by the use of the optical fibers. The injecting current from the respective laser diodes 10 is controlled by line exchange control signals from the respective terminal sides, thereby, the exchange can be realized between the desired terminals. Thereby, even when the number of the terminals is increased without using an optical demuliplexer, the good crosstalk characteristic can be provided with the low loss in the insertion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical switching system that exchanges optical signals from subscriber line optical fiber cables as they are without converting them into electrical signals.

[Conventional technology]

As optical fiber transmission becomes more widespread, the structure of optical communication networks, including switching, is being considered. In particular, the application of optical technology to subscriber line exchanges and trunk line exchanges, which are the central mates of subscriber services, is expected to have a major impact on the era of digital integration of networks, and as a form of ultimate It is desired to realize an optical switch that can exchange optical signals directly from an optical fiber cable.

Research on this optical switching system is at an early stage, but several system ideas have been proposed. These system ideas are described, for example, in Yasui and Kikuchi's ``Exploring the Possibilities of 1-Optical Computers,'' 1985 Electricity and 1-Line Information Association Conference, p.3-100 to p.3-1.03. According to the above materials, the optical exchange system is space-division type and time-division type.

There is a wavelength division type. As a specific configuration method for the wavelength division type,
It is disclosed in Japanese Patent Application Laid-open No. 103835/1983. FIG. 7 shows a conventional example of the wavelength division type.

This involves converting the wavelengths of the optical signals 11 to 1n from the incoming line into the wavelengths of the outgoing line using their respective wavelength conversion circuits, then combining them with a multiplexer and inputting them to the demultiplexer via a wavelength multiplexing transmission line. . The wavelength-multiplexed optical signal is demultiplexed (
Wavelengths λ21 to λ1. ), and an optical signal of a desired wavelength is output to each assigned outgoing line. This configuration has the advantage of being inexpensive because it eliminates the need for a switch that changes the path of light.

[Problem that the invention seeks to solve]

In the above conventional technology, since a single branching filter is used, the wavelength range λ8 that can be used includes light source manufacturing technology, optical transmission characteristics, system conditions (transmission loss, transmission band, signal-to-noise ratio, transmission distance, etc.) Considering this, there are some limitations.

Therefore, when the number n of incoming lines (or outgoing lines) increases, the wavelength interval λW (1 m
/n) is very narrow. As the wavelength interval λW becomes narrower, it becomes difficult to construct a single demultiplexer.

In other words, it becomes difficult to realize a duplexer with narrowband characteristics, and the crosstalk characteristics deteriorate due to interference between signals. Furthermore, the configuration of an optical demultiplexer that can handle several tens of wavelengths is extremely complicated, and there are problems in that the insertion loss also increases.

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to realize a wavelength division type optical switching system without using any optical demultiplexer. i.e. low insertion loss, good crosstalk characteristics? It is an object of the present invention to provide an optical switching system capable of increasing the number n of incoming lines (or outgoing lines) while maintaining the number of incoming lines (or outgoing lines).

[Means to solve all problems]

The above object is achieved by adopting the following configuration. In other words, optical signals of different wavelengths are transmitted from 41-some n terminals through optical fibers? The n optical signals are input to an n×n port type optical star coupler with n people and boats, and the output light from the output port is input to a wavelength tunable laser diode, and each laser The output light of the diode is transmitted to each terminal using an optical fiber, and the injection current of each laser diode is controlled by a circuit switching control signal from each terminal, so that it is possible to transmit the output light between the desired terminals. It is what makes exchange possible.

[Effect]

The operation will be explained using a block diagram of the wavelength division type optical switching system of the present invention shown in FIG. 101 to Ion are optical transmitting units of the respective terminals, and 111 to 11n are optical receiving units of the respective terminals. In the case of burning, each optical transmitter has a different wavelength λ1. λ2. ......, λ, is assigned. Optical signals with wavelengths λ1 to λ transmitted through the plurality of optical fiber cables 11 to ln enter the matrix type branching array 8, and a portion of each optical signal is sent to the matrix type photodetector array 91. , the remaining optical signal is sent to a so-called nXn boat type optical star coupler 9 having n input and output ports. n
Optical signals having respective wavelengths λ1 to λ, fr that are incident on the Xn boat type optical star coupler 9 are combined and mixed in this optical star coupler.

Then, optical signals having optical signal components of respective wavelengths λ1 to λ are equally distributed and transmitted to the respective output boat fibers 41 to 40. The optical signals of the respective output port fibers are input to the input end side of the matrix type wavelength tunable laser diode array 10. On the other hand, the matrix type light receiving element array 91 extracts circuit switching control signals sent from each subscriber and inputs them to the control section 92. In the control section 92, each drive current control circuit of the wavelength tunable laser diode array 10 is controlled by the above-mentioned q-line exchange control signals 71 to 7n. This control method includes, for example, transmitting an optical signal sent from the optical transmitter 102 through the optical fiber 21,
Let us consider the case where the optical receiver 111 receives the signal.

In this case, a circuit switching control signal is sent from the optical transmitter 101 to request information from the optical transmitter 102 to be sent. This line exchange control signal is received by the IJ type optical element array, and is passed through the entire control section 92 to drive the current control circuit 93.
sent to. The drive current control circuit 93 controls the wavelength tunable laser diode placed between the optical transmission lines 41 and 21.
A drive current is set so that the laser diode oscillates at a wavelength λ, and is passed through the supply line 81 to the laser diode. In this way, the wavelength λ1 . Among the optical signals of λ2..., λ,
Wavelength λ.

Only the optical signal of wavelength λ is amplified by the laser diode, and only the optical signal of wavelength λ is transmitted within the optical transmission line 21 and received by the optical receiver 111. Similarly, if you want the optical receiver 112 to selectively receive the optical signal from the optical transmitter 10n,
A current is passed through the current supply line 82 so that the wavelength tunable laser diode inserted between the optical transmission lines 42 and 22 oscillates at a wavelength λ. As described above, wavelength division light exchange is performed with a very simple configuration. There is no need to use an optical demultiplexer. Further, the wavelength tunable laser diode is, for example, T,
'If you use the C3-LD announced by Mr. psang et al.
In the range of oscillation wavelength 1.3μm±75 people, 10 people/
Because it can be changed by the mA ratio.

More than 100 wavelengths can be used (“Fast Direct Single Frequency Modulation with Large Variable Frequency Range in 03 Semiconductor Lasers”, Applied Physics Letters, 42(8), 15. April 1983).

p6so ~p652 (-High-8peed d
direct single-frequency mo
duration with large tuning
great and frequency excu
rsion in cleaved-coupled
-cavity semiconductor 1as
ers.

App'-Phys, Let t-, 42(8)p
15+ April It 1983゜[)650~p
652) ). FIG. 6 shows a structural diagram and a characteristic diagram of the C3-LD. In addition, in FIG. 2, 94 is an optical switch.

〔Example〕

FIG. 1 shows a specific configuration diagram of the front portion of the optical exchanger 94 shown in FIG. 2. In FIG. 127 is an optical fiber cable for respectively propagating information signals from a plurality of terminals, and corresponds to 11 to 1n in FIG. 2. In the embodiment shown in FIG. 1, the number of terminals is 16, and the optical fiber cables 127 are arranged in a matrix of 4 rows and 4 columns.

121 is a distributed refractive index flat plate microlens array for converting each light output signal from the optical fiber cable into parallel light, and is arranged in a 4 rows and 4 columns structure facing the output light of the optical fiber cable. There is. This distributed index flat plate microlens array is well known, and an example thereof is shown in FIG. As shown in the figure, 4 rows 4
It has a column array structure. 8 is a matrix type branch array.

A schematic diagram of its operation and a schematic diagram of its structure are shown in FIGS. 4(a) and 4(b). First, as shown in FIG. 4(a), an input optical signal P+1 with a wavelength λ1 is transmitted by the beam splitter 129 as a transmitted signal Pt1 and a reflected signal P, K:, an input optical signal P+2 with a wavelength λ is transmitted by the beam splitter 129. Signal PI2
and reflected signal Piffi, input optical signal Pta of wavelength λ
is divided into a transmitted signal Pta and a reflected signal P by a beam splitter 129, respectively. The distribution ratio between the transmitted signal and the reflected signal can be divided almost arbitrarily depending on the performance of the beam splitter. Furthermore, when the wavelength range from wavelength λ1 to λ becomes very wide, the distribution ratio of the transmitted signal and the reflected signal of the beam splitter becomes slightly wavelength dependent. Even if the wavelength range is narrowed, the influence of crosstalk is small, so the wavelength range does not become very wide. Fourth
Figure (b) is a schematic diagram of the structure of the above-mentioned matrix-type branch array, which shows triangular cedar-shaped glass blocks 130 and 131.
A beam splitter 129 is inserted between the two.

Reference numerals 122 and 123 are distributed index flat plate microlens arrays that are tightly fitted to 121, and this time they are fitted in a manner opposite to 121 to condense parallel light. 91 is a matrix type light receiving element array, and as shown in FIG. 5, 16 light receiving elements 132 are arranged in a matrix of 4 rows and 4 columns. Such a structure can be fully realized using existing technology. 9 is an optical fiber type star coupler having 16 input and output port fibers. This optical fiber type star coupler can be realized using the optical star coupler proposed by the present inventors (Imoto, Ike: Optical fiber type distribution circuit and its manufacturing method, IEICE Optical and Quantum Electronics Technology Study Group Materials, 0
QE84-107, January 1985, p81-p87)
. The input and output port fibers are arranged in a 4-by-4 structure. The principle of this optical star coupler is that, for example, an optical signal incident on one optical fiber, which is an input boat fiber, is distributed at the central part 133s of the optical star coupler, which is configured in a piconic taper shape, and each output is They are equally distributed to the output ends of the port 7 eyepers. Here, when the optical fiber is composed of a multimode fiber, there is almost no wavelength dependence in the optical star coupler distribution characteristics, but when it is composed of a single mode fiber, it has wavelength dependence. Therefore, it is desirable to make the piconical taper shape as long as possible to provide broadband wavelength characteristics. Each output port 7
Optical signals with wavelengths λ1 to λ16 are combined and outputted from the AIPA. The intensity of each emitted optical signal is approximately equal. 124 is a distributed refractive index flat plate microlens array having the same structure as 121, which converts the optical signal emitted from each output port fiber of the optical star coupler 9 into parallel light, and transmits it to the next matrix type wavelength tunable laser diode 10. It has the effect of making it incident. The matrix type wavelength tunable laser diode 10 has four rows and four laser diode elements arranged in a matrix as shown in FIG. 6(a).
It is possible to arrange them in columns. Is the laser diode element mentioned above mentioned in the previous document? Quoted at a rate of 10 people/mA by controlling the injection current.

It has been shown that as many as 150 people can change the wavelength, and it is easy to select 16 wavelengths from the 150 people as in this example (Figure 6(b)). 125 is a distributed refractive index flat plate microlens array for focusing each optical signal line-switched by wavelength selection in the wavelength tunable laser diode 10 onto each optical fiber 128;
is the same as

As described above, in the present invention, a wavelength tunable laser diode is used instead of an optical demultiplexer to selectively demultiplex optical wavelengths.
This enables more optical exchange.

Note that the present invention is not limited to the above embodiments. First, it goes without saying that a wavelength tunable laser diode other than a C"-LD may be used. Also, the number of terminals can be two or more.

〔Effect of the invention〕

According to the present invention, since no optical demultiplexer is used, even if the number of terminals (that is, the number of incoming and outgoing lines) is increased, insertion loss is low.
It is possible to realize a wavelength division optical switching system with good crosstalk characteristics.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an embodiment of the optical exchanger of the present invention, Figure 2 is a diagram showing an outline of the wavelength division type optical exchange system of the present invention, and Figure 3 is a distributed refractive index used in the optical exchanger of Figure 1. FIG. 2 is a diagram schematically showing a flat microlens array. FIG. 4 is a diagram showing the operation and structure of the matrix type branch array used in FIG. A diagram showing the structure of a tunable laser diode and its characteristics, and FIG. 7 is a diagram schematically showing a conventional wavelength division type communication path. 11~1n...Input optical fiber cable% 21~2
n...Output optical fiber cable, 31 to 3n. 41-4n...optical fiber, 51-5n, 81-8n
... Optical propagation path, 61-6n... Light-receiving element array output signal, 71-7n... Line switching control signal, 8... Matrix type branch array % 9... Nxn port type optical star capacitor, 10 ...Matrix type wavelength tunable laser diode, 91...Matrix type light receiving element array, 9
2...Control unit, 93...Drive current side #circuit, 101
~Ion... Optical transmitter, 111 - lln... Optical receiver, 127.128... Optical fiber cable, 121
~126...distributed refractive index flat plate microlens array,
129... Beam splitter, 130, 131...
Glass block, 132...light receiving element.

Claims (1)

[Claims] 1. Transmit optical signals of different wavelengths from a plurality of n terminals through optical fibers and input them to the input ports of the n×n port type optical star coupler, and input the output light from the output ports to the wavelength tunable laser diode. The output light of each laser diode is transmitted to each terminal through an optical fiber, and the injection current of each laser diode is controlled by a circuit switching control signal from each terminal side. Split type optical switching system.