JPH09139962A - Optical space switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the loss characteristic and to make it stable by coupling plural signal lights from the inside of a body with a specific optical fiber via an emission collimator array and conversing the lights into an electric signal by an O/E converter so as to shape and regenerate the waveform. SOLUTION: Each of plural signal lights radiating from a switch body consisting of plural optical path conversion elements is made incident into an emission collimator array 11 to be coupled with a multi-mode optical fiber 12. Thus, even when alignment of each part of the body is out-of-order, the propagation optical signal is coupled with the optical fiber at a high coupling efficiency and then outputted. Furthermore, an optoelectric converter 13 located in the vicinity of the array 11 converts the optical signal into an electric signal at once and the signal is given to a electrooptic converter 14, from which an optical signal to be propagated through the single mode optical fiber 6 is regenerated. In this case, the dispersion in the signal intensity is suppressed and the loss is made stable equivalently by adjusting the luminous intensity identical to all the converter 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel optical space switching circuit.

[0002]

2. Description of the Related Art A cross-connect (path switching) process for a broadband optical signal is performed by using a multi-channel spatial optical switch and performing a switching process in an optical state.
It is possible to avoid the influence of electrical crosstalk and realize simplification of processing. As a spatial optical switch for such path switching processing, a multi-channel optical switch composed of a liquid crystal spatial modulator array and a polarization beam splitter has been proposed in the past (Noguchi et al., "Optical for Ultra High-speed Optical Communication Networks"). Digital Cross-Connect System Laboratory Experiment ", IEICE Technical Report, OSC93-40, pp. 25-31, (1993)).

FIG. 1 shows the configuration of a conventional liquid crystal multi-channel optical switch. In the figure, 1 is a plurality of single mode optical fibers for inputting an optical signal, and 2 is an optical signal input collimator array for converting an optical signal propagating through the single mode optical fiber 1 into collimated light and inputting it into the switch body. Is. Further, 3-1 to 3- (n + 1) are polarization routing elements having a function of shifting only the emission position of one linearly polarized component of the incident collimated light signal, and 4-1 to 4-n are the incident collimated light. A liquid crystal optical modulator having a function of individually switching linearly polarized light components of signals that are orthogonal to each other for each incident collimated light, and these constitute a switch body. Reference numeral 5 denotes an optical signal output collimator array that collects the collimated optical signal that has passed through the switch main body and outputs it again to the outside of the switch main body as propagating light of a plurality of single mode optical fibers 6 for outputting an optical signal. Is.

With the above configuration, the collimated optical signals incident from the optical signal input collimator array 2 are orthogonal to each other by the polarization routing element 3-1.
It is separated into two linearly polarized light components. These optical signals are respectively shifted to target emission positions by the liquid crystal light modulators 4-1 to 4-n and the polarization routing elements 3-2 to 3-n which are alternately arranged. First, the polarization routing element 3-
The two orthogonal polarization components of the same optical signal separated by 1 are combined by the polarization routing element 3- (n + 1) and coupled to the target collimator of the optical signal output collimator array 5.

The optical space switching circuit according to this configuration is
Since the optical input / output collimator can be two-dimensionally arranged in the space, a multi-channel switch can be easily formed as compared with the optical switch formed on the waveguide.

In addition, a prism or a mirror is installed instead of the polarization routing element and the liquid crystal light modulator, and the optical path of the emitted collimated light is changed by moving or rotating the prism or the mirror to couple it to a target collimator. An optical space switching circuit similar to the above is also configured by using the switch body.

[0007]

However, in the above-described optical space switching circuit, since the spatial propagation distance of the signal light is long, the signal light is output as an optical signal due to a slight misalignment of each part of the switch body. The loss at the time of coupling to the collimator increases, and the coupling loss changes greatly depending on the connection destination. For this reason,
There is a drawback that stable operation as an optical space switching circuit is likely to be impaired.

An object of the present invention is to stabilize and reduce loss characteristics in an optical space switching circuit.

[0009]

In order to solve the above-mentioned problems, according to claim 1 of the present invention, in an optical space switching circuit provided with a switch body composed of a plurality of optical path changing elements, a plurality of light beams are emitted from inside the switch body portion. An output collimator array that couples each of the signal lights of (1) to a multimode optical fiber, and an optical-electrical converter that individually converts the optical signals that are coupled to the optical fibers into electrical signals, and shapes and reproduces the signal waveform. We propose an optical space switching circuit with and.

According to the above construction, the optical signal output collimator array is changed from the conventional one for coupling with a single mode optical fiber to one for coupling with a multimode optical fiber. Even if the deviation occurs in the optical fiber, the optical signal propagating in the switch body can be coupled to the optical fiber with high coupling efficiency and output outside the switch body.

Further, according to a second aspect of the present invention, in the optical space switching circuit having the switch main body composed of a plurality of optical path changing elements, each of the plurality of signal lights emitted from the inside of the switch main body is individually converted into an electrical signal. We propose an optical space switching circuit equipped with an opto-electrical conversion unit that converts the signal into an optical signal and shapes and reproduces the signal waveform.

According to the above construction, since the plurality of signal lights emitted from the inside of the switch main body are individually provided with the opto-electrical converters as the light receiving elements for individually converting them into electric signals, the respective parts of the switch main body are provided. Even if the alignment is misaligned, the optical signal propagating in the switch body can be coupled to the light receiving element with high coupling efficiency and output as an electric signal outside the switch body.

According to a third aspect of the present invention, in the optical space switching circuit according to the first or second aspect, each of a plurality of signal lights propagating through a single mode optical fiber is provided in a switch body. We propose an optical space switching circuit with multiple incident multimode optical fibers.

According to the above construction, an optical signal from a single mode optical fiber having a small core diameter and a small relative refractive index difference is coupled to a multimode optical fiber having a large core diameter and a large relative refractive index difference, and is coupled to the switch body. Since it is incident, the coupling loss on the input side can be made extremely small.

Further, in claim 4 of the present invention, claim 1
In the optical space switching circuit according to any one of items 1 to 3, there is proposed an optical space switching circuit including an electro-optical conversion unit that converts an output electric signal of the opto-electric conversion unit into an optical signal again and outputs the optical signal.

According to the above configuration, the O / E converter and the E / O
The loss can be stabilized by the action of the converter.

[0017]

FIG. 2 shows an embodiment of the present invention. In the figure, the same components as those of the conventional example are designated by the same reference numerals. That is, 1 is a single mode optical fiber for inputting an optical signal, 2 is an optical signal input collimator array, and 3-1 to 3-3-
(N + 1) is a polarization routing element, 4-1 to 4-n are liquid crystal optical modulators, 6 is a single-mode optical fiber for outputting an optical signal, and 11 is polarization routing elements 3-1 to 3- (n + 1).
And an optical signal output collimator that collects the collimated optical signal that has passed through the switch body composed of the liquid crystal light modulators 4-1 to 4-n, couples it to the multimode optical fiber 12, and outputs it to the outside of the switch body. An array, 13 is an O / E converter for converting an optical signal into an electric signal, and 14 is an E / E converter for converting the electric signal into an optical signal propagating through the single mode optical fiber 6.
It is an O converter.

One of the features of the present invention is that the optical signal output collimator array 11 is changed from a conventional single mode optical fiber coupling type to a multimode optical fiber 12 coupling type. As a result, even if misalignment occurs in each part of the switch body, the optical signal propagating in the switch body can be coupled to the optical fiber with high coupling efficiency and output outside the switch body.

The optical signal coupled to the multimode optical fiber 12 is distorted in the signal waveform due to the effect of mode dispersion propagating in the fiber over a long distance. In addition, when the multimode optical fiber propagating light is coupled to the single mode optical fiber, a large loss occurs, and the optical intensity fluctuates due to the effect of mode distribution noise. Therefore, the optical signal output collimator array 11
The signal light coupled to the multimode optical fiber 12 via
The O arranged near the optical signal output collimator array 11
Once converted to an electric signal by the / E converter 13, E / O
The converter 14 regenerates the optical signal propagating through the single mode optical fiber 6 again.

At this time, the finally output optical signal is E /
The light source of the O converter 14 is modulated. Therefore, if the emission intensity is adjusted to be the same for all E / O converters, the variation in the optical signal intensity for each channel is greatly suppressed, and the loss is equivalently stabilized. Becomes The wavelength of the optical signal is the wavelength of the light source of the E / O converter 14, and may be different from the wavelength of the optical signal received by the O / E converter 13. Therefore,
By inserting the O / E converter 13 and the E / O converter 14, wavelength conversion as well as optical signal path switching can be performed simultaneously.

FIG. 3 shows another embodiment of the present invention, which is a polarization routing element 3- in the final stage of the switch body.
Each of a plurality of signal lights emitted from (n + 1) is directly coupled to the O / E converter 13 as a light receiving element, and other configurations and operations are similar to those of the embodiment shown in FIG. .

If the E / O converter 14 is removed from the optical switch configuration of FIGS. 2 and 3 and the electrical signal output of the O / E converter 13 is terminated, the output of the optical switch is converted into an optical signal. It is possible to realize a configuration in which the signal is terminated as it is without being sent out. Further, in the example of FIGS. 2 and 3, the liquid crystal type is used as the switch main body, but it goes without saying that a mechanical type may be used.

FIG. 4 shows still another embodiment of the present invention. In the figure, 21-1 to 21-n are single-mode optical fibers for inputting optical signals, 22-1 to 22-n are optical space switch input multimode optical fibers, and 23 is multimode optical fiber propagating optical signals. Multi-channel optical space switch for switching, 24-1 to 24-n are optical space switch output multi-mode optical fibers, 25-1 to 25-n are opto-electric conversion circuits for converting optical signals into electric signals, 26- 1-2
6-n is a light intensity modulator that modulates the intensity of passing light according to an input electric signal, 27-1 to 27-n are light sources that emit continuous light, and 28-1 to 28-n are for outputting optical signals. Is a single mode optical fiber.

Single-mode optical fibers 21-1 to 21-n
Optical signals incident from the outside via the optical couplers are coupled to the optical space switch input multimode optical fibers 22-1 to 22-n, respectively. The coupling loss at this time is the coupling from the single mode optical fiber (core diameter 10 μm, relative refractive index difference 0.3%) to the multimode optical fiber (core diameter 50 μm, relative refractive index difference 1.0%). Therefore, it becomes very small.

Optical space switch input multimode optical fiber 2
The optical signal that has entered the multi-channel optical space switch 23 via one of 2-1 to 22-n has its optical path switched in the optical space switch 23 according to its destination, and the optical space switch outputs the multimode optical fiber. 24-1 to 24-n.

The influence of the axial deviation and the angular deviation of the optical path when the optical signal that has passed through the optical space switch is coupled to the output optical fiber has an influence on the coupling efficiency, because the core diameter of the output optical fiber and the relative refractive index difference are both. The larger it is, the smaller it can be. Therefore, by using a multimode optical fiber as the fiber that guides the output optical signal from the optical space switch, compared to an optical switch configured with a single mode optical fiber,
The requirements for the mechanical and optical accuracy of the switch component can be greatly relaxed.

Optical space switch output multimode optical fiber 2
The optical signals guided to the 4-1 to 24-n are converted into electric signals by the optical-electrical conversion circuits 25-1 to 25-n, and the optical signals are respectively driven to the optical intensity modulators 26-1 to 26-n. To do. On this occasion,
The light emitted from the continuous light sources 27-1 to 27-n is
Each is intensity-modulated by the light intensity modulators 26-1 to 26-n, reproduces the optical signal waveform incident on the optical-electrical conversion circuits 25-1 to 25-n, and the single mode optical fiber 28-
It is sent to the outside of the device via 1 to 28-n.

In this configuration, the electro-optical converting section is configured to modulate continuous light from the light source according to the output electric signal of the opto-electric converting circuit. Therefore, if the input optical signal is a digital signal, the spontaneous emission optical noise generated by the optical amplifiers connected in multiple stages on the optical transmission line is controlled by a limiter amplifier or comparator for the electrically reproduced signal. It can be easily removed by using it. At this time, a band sufficient for a circuit such as a limiter amplifier (a bit rate of the transmitted optical signal is 1.5 to
2 times), without synchronizing the clock of the signal,
No degradation of signal quality is observed. Therefore, it is not necessary to provide a clock synchronization circuit in the optical-electrical conversion circuits 25-1 to 25-n, and the circuit can be simplified.

Although the intensity modulator is used as the modulator in this example, if the phase-modulated light is required in the subsequent stage, the intensity modulator may be used as the phase modulator and the frequency-modulated light is required. In that case, the light source and the modulator emitting continuous light may be replaced with a semiconductor laser, and the electric signal may be superimposed on the bias current.

[0030]

As described above, according to the present invention,
Stabilization and reduction of the loss characteristics of the optical space switching circuit are achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a conventional optical space switching circuit.

FIG. 2 is a configuration diagram of an optical space switching circuit showing an embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical space switching circuit showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical space switching circuit showing still another embodiment of the present invention.

[Explanation of symbols]

1, 6, 21-1 to 21-n, 28-1 to 28-n ... Single mode optical fiber, 2 ... Optical signal input collimator array, 3-1 to 3- (n + 1) ... Polarization routing element, 4
-1 to 4-n ... Liquid crystal light modulator, 11 ... Optical signal output collimator array, 12, 22-1 to 22-n, 24-1 to 2
4-n ... Multimode optical fiber, 13 ... O / E converter, 1
4 ... E / O converter, 23 ... Multi-channel optical space switch, 25-1 to 25-n ... Optical-electrical conversion circuit, 26-1
26-n ... Light intensity modulator, 27-1 to 27-n ... Light source.

Claims (4)

[Claims] 1. An optical space switching circuit having a switch body composed of a plurality of optical path changing elements, wherein each of a plurality of signal lights emitted from the inside of the switch body is
An output collimator array to be coupled to the multimode optical fiber, and an optical-electrical converter for individually converting the optical signal to be coupled to the optical fiber into an electric signal and shaping and reproducing the signal waveform. Characteristic optical space switching circuit. 2. An optical space switching circuit having a switch body composed of a plurality of optical path changing elements, wherein each of a plurality of signal lights emitted from the inside of the switch body is
An optical space switching circuit, characterized by comprising an optical-electrical conversion unit for individually converting into an electric signal and shaping and reproducing the signal waveform. 3. A plurality of multi-mode optical fibers for injecting each of a plurality of signal lights propagating through the single-mode optical fiber into the switch main body portion. The optical space switching circuit described. 4. The optical space switching circuit according to claim 1, further comprising an electric-optical conversion unit that converts an output electric signal of the optical-electric conversion unit into an optical signal and outputs the converted optical signal. .