JPS617739A - Optical switching circuit - Google Patents

Abstract

PURPOSE:To realize a low-input loss optical switching circuit, by installing a light-to- electricity converting means and electricity-to-light cnverting means to an optical branching path and controlling both the converting means in accordance with control signals, and then, setting the light emitting wavelength of the electricity-to-light converting means to different values at every optical branching path. CONSTITUTION:Optical signals transmitted from input light transmitting paths 3a and 3b are branched by means of optical branching paths 21a and 21b and made incident to light-to-electricity converting means 25a-25d. Electric signals which are the outputs of the converting means 25a-25d are respectively amplified by amplifiers 26a- 26d and supplied to electricity-to-light converting means 27a-27d. The amplifiers 26a- 26d and converting means 27a-27d are controlled by a control circuit 5. Outputs of the converting means 27a-27d are combined by means of interference film filters 1a and 1b by utilizing their wave lengths being different from each other, after the wavelengths of the converting means 27a-27d are set to different values and the outputs of the converting means 27a-27d are made parallel with each other. Then the optical beam thus combined is efficiently coupled with output transmitting paths 4a and 4b through lenses 2a and 2b and this optical switching circuit is made low in input loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical switch circuit that arbitrarily switches connections between multi-channel optical transmission lines.

(Prior art and its problems) With the full-scale commercialization of optical communication systems in recent years, systems that provide new functions and services not available in the past are being considered. An example of a device required in such a system is an optical switch circuit that switches connections between a large number of optical transmission lines at high speed. Conventionally, so-called mechanical type optical switch circuits that move prisms, lenses, or the optical transmission line themselves have been widely used, but improvements such as high switching speed, operational reliability, and multichannelization have been widely used. Considering the requirements, it is thought that non-mechanical switch circuits that can be integrated will become mainstream in the future. One such optical switch circuit is known as an optical branch/optical gate type switch circuit, as shown in Japanese Patent Application No. 56-196279. The configuration and operation of this optical branching/optical gate type switch circuit will be explained.

FIG. 1 is a diagram for explaining the operation of the optical branching/optical gate type switch circuit. Here, for simplicity, 2
The case of two human outputs is shown. Two input optical transmission lines 3
The optical signals transmitted by a j3b are each sent to optical branch 2.
1aj21b, and the optical signal from the optical branch 21a is sent to the optical gate switch 22aj22b, and the optical signal is sent to the optical branch 21b.
The optical signals from the optical gates enter the optical gate switches 22c and 22d, respectively. Here, the optical gate switch is an optical modulator type switch that turns off the passage of an optical signal by 0Np according to a control signal. If the optical gate switch is in the ON state, the optical signal passes through as is, and if it is in the OFF state, the optical signal does not pass through the optical gate switch and stops there. The output waveguide is a multiplexing waveguide (see FIG. 1), and only the signal from the input optical transmission line 3a passing through the optical gate switch 22a or 22c is output. On the other hand, the optical signal from the input optical transmission line 3b is multi-branched by the optical branch 21b, and only the optical signal branched toward the optical gate switch 22c that is in the ON state passes through, and is output first through the output optical waveguide 23a. If you want to output the optical signal from 3b to the optical output 24b, turn each optical gate switch 22a-ON*22b-OFFp22c
It is sufficient to keep it in the mOFF+22d-ON state. As described above, the optical gate switches 22a j22b j22c
By switching ON-OFF of z 22d, the optical signal of the input optical transmission line 3aj 3b and the optical output 24a are
p24b switching can be realized. In addition, each optical gate switch is 22a-ONy22b-ONy22cm
When OFFj22d-OFF is maintained, the optical signal from the input optical transmission line 3b is not output, and the optical signal from the input optical transmission line 3a is outputted as two optical outputs 24aνt=24b7. In this manner, this configuration has the function of distributing optical signals in addition to switching the connection of optical signals υ. This optical switch circuit structure has the advantage that it does not deteriorate the band p quality of the transmission signal and there are no problems with electromagnetic induction or crosstalk compared to the method. Furthermore, there are conventional waveguide-type switches that switch optical paths (for example, directional coupler-type optical switches that utilize electro-optic effects).

) Optical gate switches are suitable for multi-channel applications because they can be made smaller. As described above, the optical branching/optical gate type switch circuit has excellent welfare in principle.

In the optical branching/optical gate type switch circuit, since the output light from the original gate switch is multiplexed, the signal light that has not been completely extinguished by the optical gate switch in the OFF state is mixed in as a crosstalk component. This effect increases as the number of channels increases. Therefore, an optical gate switch is required to have a large extinction ratio in addition to the requirements for small size and high speed. As a conventional optical gate switch, 1
2) Using the Franz-Kjeldzy effect; 3) Using liquid crystals (using scattering or electro-optic effects; 4) Modulating gain and loss by injecting carriers into the semiconductor. They were thinking of things to do. Among these, for 1) to 3), the experimentally obtained extinction ratio is about 20 to 30 dB, which is not sufficient. Among 4), a so-called semiconductor laser switch that controls current injection into a semiconductor laser has an extinction ratio of 60 to 70d.
B has been obtained, but since the gain mechanism of the semiconductor laser is used, the characteristics are influenced by the mode and wavelength of the incident light.
Switching of multi-mode fiber light involves a photoelectric conversion means for converting into an electrical signal, an electro-optic conversion means for converting the electrical signal output from the photo-electric conversion means back into an optical signal and outputting it, and a photo-electric conversion means and an electro-optic converter according to a control signal. It has already been proposed to configure the converter with means for controlling the operation of the converting means (repeater configuration).

In this case, since amplification and waveform shaping are possible at the electrical signal level, it is possible to compensate for loss due to optical branching, and a very high extinction ratio of the optical signal can be expected. There is still the advantage that switching operation can be obtained regardless of the mode and wavelength of the incident light.

However, such optical switch circuits have the following problems. In order to actually obtain operation as a multi-channel switch, a multiplexing waveguide is required as explained using FIG. However, if you try to combine light by using a simple 1:n optical branch in reverse, you will have to achieve perfect mode matching between the multiple optical signals to be combined and the single waveguide to which they are combined. Failure to do so will result in large losses.

Therefore, even if the optical level is regenerated through the -I electrical signal within the optical gate switch, the optical transmission distance after the optical switch is limited due to loss in the multiplexing waveguide. The problem arises that it is lost.

(Object of the Invention) The object of the present invention is to eliminate the drawbacks of the above-mentioned optical branching/light gate type optical switch circuit, to be compact and suitable for integration, and to enable high-speed switching without distorting broadband signals with low crosstalk. An object of the present invention is to provide an optical switch circuit that takes advantage of the optical branching/optical gate type optical switch circuit, which is capable of switching multi-mode fiber light, and has low insertion loss.

(Structure of the Invention) According to the present invention, light entering from one input end is m(≧
2) Optically connected in cascade to m (≧1) optical branches that branch into main beams and each branch destination of the optical branches, and has a function of allowing light to pass in the ON state and not allowing light to pass in the OFF state. The output light of the optical branch is electrically connected to the switch, which is composed of a switch and an output waveguide connected vertically to each of the switches, and has the function of passing light in the ON state and blocking light in the OFF state. A photoelectric conversion means for converting into a signal, an electro-optic conversion means for converting the output of the photo-electric conversion means into an optical signal again and outputting it to the output waveguide, and operation of the photo-electric conversion means and the electro-optical conversion means in accordance with a control signal. The present invention provides an optical switch circuit including a plurality of means for controlling the light, wherein the light emission wavelength of the electro-optical conversion means is made different for each of the optical branches.

(Detailed explanation of the structure) FIG. 2 is a diagram for explaining the present invention in detail. Here again, for the sake of simplicity, we will explain the case of two people and two outputs.

The optical signals transmitted through the two input optical transmission lines 3a and 3b are branched into optical branches 21ap and 21b, respectively, and enter the optical gate switch.

Here, each optical gate switch is a photoelectric conversion means 25aj
25by25c*25dt Electrical signal shaping and amplification system 26
as26bt26cj26d, electric light conversion means 27a p
27b p 27c t 27d. The electro-optical conversion means is specifically composed of LllLEDs, but the oscillation wavelength thereof can be arbitrarily selected as long as the entire system is not wavelength multiplexed. Therefore, the wavelength can be made different for each optical branch 21aj21b. In other words, the electric light conversion means 27a y 27b and 27c p
The wavelength of 27d is different. By doing this, in order to realize an optical switch circuit, for example, when combining the output lights of the electro-optical conversion means 27a, 27cj, 27b and 27d, the wavelengths of the two combined lights are different, so this is used to create interference. It can be combined with low loss using films, gratings, etc. Therefore, with such a configuration, it is possible to realize an optical switch circuit with low insertion loss while taking advantage of the advantages of the conventional optical branching/optical gate type optical switch circuit.

(Example) Examples of the present invention will be described in detail below with reference to the drawings. FIG. 3 is a schematic diagram showing an embodiment of the optical switch circuit according to the present invention. Here again, for the sake of simplicity, we assume a 1 μm band optical transmission system and explain the case of 2 outputs by 2 people. The optical signals transmitted through the input optical transmission lines 3a+3b are branched by optical branches 21a-21b using couplers that are heat-sealed in close proximity to the fibers, and then split into InGaAsP fibers.
The light enters a photoelectric conversion means 25ay25by25cy25d consisting of an InP photodiode and a FET preamplifier.

Photoelectric conversion means 25a y 25b y 25c p 2
The electrical signals output from 5d are sent to amplifiers 26aj26b, respectively.
Drive circuit and In
Electro-optical conversion means 27a s 27b y 27c p 2 composed of GaAsP/InP semiconductor laser (LD)
Run 7d. Lightning conversion means 27a j27b p
InGaAsP/In used for 27c t27d
In PLD, by changing the composition, 1.2 to 1
．． The oscillation wavelength can be changed within 55 μm. Here, the wavelength of the electro-optical conversion means 27a p27c is ~1.2μ
The wavelength of m127b+27d was set to ~1.3 μm. Lightning conversion means 27a'tsu 27b y 27c j27
The output light of d is transmitted through lens 28aj28b j28c p 2
The light beams are collimated by 8d and multiplexed by interference film filter 1aylb by making the optical axes coincide with each other by utilizing the difference in wavelengths.

The two combined beams are efficiently coupled to a multi-output optical transmission line 4ap4b by a lens 2aν2b. The operation as an optical switch circuit is as follows: amplifier 26ap26bj2
Gate signal to the FET gate switch inserted between stages of 6c j27d and electro-optical conversion means 27aj27b -
A bias voltage to the LDs of 27c p and 27d was supplied from the control device 5 according to the desired switch state.

In such a configuration, the electric light conversion means 27a+27by27
The loss when combining the c*27d output light can be extremely reduced. Therefore, it is possible to provide a high margin for loss in the entire optical transmission system, and it is possible to increase the transmission distance and improve reliability. Here, an interference film filter was used as a means of combining light using differences in wavelength, but if a grating is used, it is possible to combine many lights with even closer wavelengths because of its high wavelength resolution. This is advantageous for increasing the number of channels in the switch circuit. Further, if a waveguide wavelength multiplexer having a structure in which a grating is formed on a waveguide is used for multiplexing, the device can be made smaller and more integrated. Furthermore, if an InGaAsP/InP-based waveguide wavelength multiplexer is used as the material, the electro-optical conversion means 27a, j27b
It also becomes possible to monolithically integrate the I27c and 27d LDs.

(Effects of the Invention) As described above in detail, the present invention is compact and suitable for integration, enables high-speed switching without distorting broadband signals with low crosstalk, and is also capable of switching multimode fiber optics. By taking advantage of the advantages of the optical branching/optical gate type optical switch circuit, an optical switch circuit with low insertion loss can be obtained, which will greatly contribute to the realization of various optical systems in the future.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the operation of the optical branching/optical gate type optical switch circuit, FIG. 2 is a diagram for explaining the configuration of the optical switch circuit according to the present invention, and FIG. 3 is a diagram for explaining the optical switch according to the present invention. FIG. 2 is a diagram for explaining an example of a circuit. In the figure, 18F1b is an interference film filter, 2aj2b
s 28'a p 28b r 28c j28d is a lens, 3ay3by4a+4b is an optical transmission line, 5 is a splitting circuit, 21aj21b is an optical branch, 22a y 22b +
22c y 22d is an optical gate, 23aJ23b is an output waveguide, 24aj24b is a laser beam, 25a-25b+
25c+25d is photoelectric conversion means, 26ap26b j2
6c j26d is amplifier, 27a927by27cy2
7d is an electro-optical conversion means. Figure 1 Figure 2

Claims (1)

[Claims] n (≧1) optical branches that branch light entering from one input end into m (≧2) beams, and optically cascaded to each branch destination of the optical branches. When connected and ON, light passes through and O
The switch is composed of a switch that has the function of not allowing light to pass through in the FF state, and an output waveguide that is vertically connected to each of the switches, and has the function of passing light in the ON state and blocking the light in the OFF state. a photoelectric conversion means for converting the output light of the optical branch into an electric signal; an electro-optical conversion means for converting the output of the photoelectric conversion means back into an optical signal and outputting it to the output waveguide; an optical switch circuit comprising means for controlling the operation of the photoelectric conversion means and the electro-optical conversion means, wherein the light emission wavelength of the electro-optical conversion means is made different for each of the optical branches. circuit.