JP2000075168A - Parallel optical transmission device and parallel optical transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a parallel optical transmission device which facilitates the alignment of optical parts and has less skew by forming periodic light intensity distributions at the incident end of an optical fiber array and making light incident on optical fibers. SOLUTION: The beam emitted from a laser array 10 passes a lens array 20 having lenses of the same number of pieces as the number of pieces of lasers, further passes a prism array 30 having triangular prisms of the same number of pieces as the number of pieces of the lasers and is made incident on the optical fiber array 50. The optical fiber array 50 is formed by assembling about 10000 pieces of single mode optical fiber cores of, for example, a core diameter of 10 μm to form one optical fiber cable and filling up the spaces among the cores with clads. The relative positions between the optical fibers are maintained up to an exit end. The incident light is, therefore, confined and transmitted in the individual core and the light intensity distributions at the incident end 52 are transmitted as they are to the exit end 54. The beam emitted from the optical fiber array 50 passes a lens 60 and is detected by a photodetector array 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to parallel optical communication using optical fibers, and more particularly, to a parallel optical transmission device and a parallel optical transmission method using an optical fiber array.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 7-114431 discloses an optical coupling bus capable of executing input / output of signals required for high-speed processing of a processor using a bundled optical fiber.

Further, Japanese Patent Laid-Open No. 8-237205 discloses a parallel optical connection device using a fiber image guide including a bundle type optical fiber for performing bit parallel data communication.

[0004]

In a conventional parallel optical transmission device, a beam from a light source array is incident on one end of an optical fiber array through optical components such as a microlens array, a lens, and a fiber taper. Light emitted from the other end is detected by a photodetector array through optical components such as a microlens array, a lens, and a fiber taper. Therefore, when assembling the parallel optical transmission device, a beam from a specific light source is accurately incident on a minute core of a corresponding optical fiber using a lens array, and an output beam from the optical fiber array is incident on a photodetector array. Such a precise alignment adjustment was necessary, and it took a long time to assemble. Further, in the conventional parallel optical connection device, there is a problem that skew occurs between optical signals transmitted through different optical fibers of the optical fiber array, so that the transmission distance cannot be lengthened.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object of the present invention is to provide a parallel optical transmission device and a parallel optical transmission system which can easily align optical components and have little skew. To provide.

[0006]

In order to achieve the above object, the present invention comprises two or more light sources and a modulation optical element for spatially modulating signal light from the light sources, respectively.
An optical transmission module for transmitting the signal light, an optical fiber for transmitting the signal light, a conversion optical element for converting the signal light from the optical fiber to a spatial frequency,
And a light receiving module for receiving the signal light.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a parallel optical transmission device according to the present invention will be described below with reference to FIG. The beam emitted from the laser array 10 passes through the lens array 20 having the same number of lenses as the laser, and further passes through the prism array 30 having the same number of triangular prisms as the laser, and enters the optical fiber array 50. The optical fiber array 50 used in the present embodiment is a single optical fiber cable having a diameter of 1 mm by bundling about 10,000 single mode optical fiber cores having a core diameter of 10 μm, and has a lower refractive index between the cores than the core. It is filled with a clad, and the relative position between the optical fibers is maintained up to the emission end. Therefore, the light incident on the optical fiber array 50 is confined in the individual cores and transmitted, and the light intensity distribution at the incident end 52 remains unchanged at the output end 5.
4 is transmitted. The beam emitted from the optical fiber array 50 passes through the lens 60 and is detected by the photodetector array 40.

The configuration of the optical transmission side and the function of each optical component will be described in more detail with reference to FIG. As the laser array 10 of this embodiment, a surface emitting laser array in which four surface emitting lasers are formed on the same substrate is used. The beam from the laser 12 is made substantially parallel by the lenses 22 in the lens array 20 and enters the triangular prism 32 in the prism array 30. The triangular prism 32 has two slopes, and each slope is formed with a slope angle and a tilt direction such that beams refracted by the slopes overlap at the incident end 52 of the optical fiber array 50. The beams separated by the triangular prism 32 and superposed at the incident end 52 of the optical fiber array 50 interfere with each other to form a periodic stripe-like intensity distribution. Similarly, the beam from the laser 14 is made substantially parallel by the lens 24 and enters the triangular prism 34. The ridge of the triangular prism 34 is approximately 4
5 °, the incident end 52 of the optical fiber array 50
The interference fringes formed are rotated by 45 ° from those formed by the triangular prism 32. As described above, in the prism array 30 of the present embodiment, the directions of the ridges of the triangular prism of each cell are different from each other by approximately 45 °.

A surface emitting laser is a semiconductor laser that emits light in a direction perpendicular to a substrate, and it is easy to form a laser array in which lasers are two-dimensionally arranged as in this embodiment. In addition, the surface emitting laser has a wide modulation band and can be used for transmission over a wide band. However, the light source of the present invention is not limited to the surface emitting laser array, and may be appropriately selected according to the configuration of the edge emitting laser array or the like.

Next, detection of an optical signal on the optical receiving side will be described with reference to FIG. The beam emitted from the emission end 54 of the optical fiber array 50 passes through the lens 60 and is detected by the photodetector array 40. The photodetector array 40 has a distance f from the lens 60 when the focal length of the lens 60 is f.
Put away. At this time, the light intensity distribution at the emission end 54 is Fourier transformed by the lens 60 and projected on the photodetector array. That is, the lens functions as a conversion optical element that converts signal light into a spatial frequency. Therefore, the beam which periodically changes in intensity in the radial direction transmitted through the optical fiber array 50 is Fourier-transformed by the lens 60 and projected on the photodetector array 40 as linearly arranged bright spots 70. The direction in which the bright spots 70 are arranged is the direction in which the stripes are arranged, and the interval between the bright spots 70 is inversely proportional to the period of the stripes. The position of the photodetector array 40 is adjusted so that the bright spot 70 fits in the photodetector. By selecting the focal length of the lens 60, the bright spot 70 on the photodetector array 40
Can be adjusted. In this embodiment, four interference fringes having different fringe directions are incident on the optical fiber array 50, and each fringe is Fourier-transformed as a different luminescent spot 70 and detected by another photodetector. In the present embodiment, optical signals are separated and detected by using eight photodetectors in the peripheral part which is divided vertically and horizontally into three parts. Note that all the fringes form bright spots at the center of the photodetector array 40 and are not used for signal detection.

Next, reproduction of a signal detected by the photodetector array 40 will be described with reference to FIG. The bright spots 70 formed on the photodetector array 40 are linearly arranged in the same direction as the direction of the stripe at the emission end. This primary (the bright spot at the center is 0
The following bright spot 70 is detected, and the signal is reproduced. The bright spots 70 formed on the photodetector 41 and the photodetector 45 are formed by the same stripe. After the signals detected by these detectors are passed through a preamplifier (not shown), the adder 100 adds the signals to obtain a signal. Other fringes form similar bright spots 70 in different directions and the photodetectors 42
And the photodetector 46, the photodetector 43 and the photodetector 47, and the photodetector 44 and the photodetector 48. The electric signals from the respective photodetectors can be summed, and the remaining three independent optical signals can be reproduced.

In this embodiment, the optical fiber array 50
The incident beam to the incident end 52 may be irradiated to the incident end 52 with a certain area or more.
Alignment with 0 does not have any particular accuracy. Also in the photodetector array 40, it is sufficient that the bright spot 70 enters the predetermined photodetector, and particularly strict alignment is not required. Therefore, the assembly of the parallel optical transmission device does not require any particular adjustment, and the optical components may be arranged within the mechanical accuracy. In the conventional parallel optical transmission device, it is necessary to align the optical fiber array with the semiconductor laser array and the optical fiber array with the photodetector array with very high accuracy.
Adjustment was required. Alternatively, for example, using an expensive Si substrate provided with a V groove, the optical fibers are arranged so that the distance between the optical fibers is constant.
Further, in this embodiment, since each optical signal transmitted in parallel is transmitted through a plurality of optical fibers,
The characteristics of each optical fiber core are averaged, and the skew between optical signals transmitted in parallel is small. Further, in a conventional parallel optical transmission device using an optical fiber array, since a signal is incident on one optical fiber, even if minute dust having a core diameter (about 10 μm) adheres to the end of the optical fiber, light is not emitted. Although light is incident on the entire optical fiber array having a large diameter as in this embodiment, even if a minute dust or dirt adheres to the end face of the optical fiber and a part of the light is interrupted, Since the signal is transmitted, there is also a feature that reliability is improved.

As described above, the present invention is characterized in that a periodic light intensity distribution is formed at the incident end of an optical fiber array and the light is incident on an optical fiber. The optical modulation means for spatially modulating the distribution is not limited to the lens array and the prism array of the present embodiment. For example, a mask having a transmittance distribution that forms a periodic intensity distribution without using a prism array may be used. The spatial modulation may modulate not only the light intensity but also the phase or both the light intensity and the phase.

In this embodiment, the lens array 2
Although 0 and the prism array 30 are used, the prism array 30 may have a light collecting function without using the lens array 20. In this embodiment, four independent light signals are transmitted using four light sources. However, the direction of the ridge of the prism of the prism array is further increased, and the number of corresponding light sources and photodetectors is increased. Thereby, the multiplicity can be further increased. In this embodiment, only the primary light is detected. However, if higher-order light is also detected, the detected light amount increases.

Next, an embodiment of the parallel optical transmission module of the present invention will be described with reference to FIGS. FIG. 5 shows a sectional view of the optical transmission module. Light emitted from the laser array 10 passes through the lens array 20 and the prism array 30,
The light enters the optical fiber array 50. Laser array 10
Is a circuit board 110 including a drive circuit of the laser array 10.
, And a data input terminal 120 for signal input comes out of the circuit board 110. The laser array 10 and the circuit board 110 are housed in a case 202. Case 2
02 is provided with a female connector 230 and a ferrule receiver 212. A ferrule 210 and a male connector 220 are fixed to the incident end 52 of the optical fiber array 50. By inserting male connector 220 into female connector 230, ferrule 210 is inserted into ferrule receiver 212.
And the incident end of the optical fiber array 50 is positioned at a predetermined position with respect to the laser array 10.

FIG. 6 is a sectional view of the optical receiving module.
The photodetector array 40 includes a circuit board 112 including a detection circuit.
, And a data output terminal 122 for signal output comes out of the circuit board 112. The light emitted from the optical fiber array 50 passes through the lens 60 and is projected onto the photodetector array 40. The photodetector array 40 and the circuit board 112
It is housed in a case 202. The case 202 is provided with a female connector 232. By inserting the male connector 222 into the female connector 232, the emission end 54 of the optical fiber array 50 is positioned at a predetermined position with respect to the photodetector array 40. . It is necessary to assemble the connector by adjusting the position of the optical fiber array 50 so that the bright spot Fourier-transformed by the lens 60 is incident on a predetermined photodetector.
Since the rotation is only 0, the adjustment is easy and can be performed in a short time. After the adjustment, the optical fiber array 50 and the male connector 222
Is fixed.

As in this embodiment, the optical fiber array 50
Is used, the alignment accuracy between the light source array and the photodetector array and the optical fiber array 50 is reduced, so that the optical fiber array 50 and the optical transmission module can be connected by a connector. Since the optical fiber array 50 can be inserted and removed from the module, the optical fibers can be replaced and the length can be adjusted. However, the relative position between the optical fiber array 50 and the photodetector array needs to be determined in advance, and when connecting the connector and the optical fiber, the relative position is determined and fixed. By using a connector that does not rotate, the relative positions of the optical fiber array 50, the laser array 10, and the photodetector array 40 do not change even if the connector is connected or disconnected.

[0018]

As described above, according to the present invention, it is possible to provide a parallel optical transmission device which has a large tolerance for positional adjustment between an optical fiber array and a light source array / photodetector array, and is easy to assemble. Was.

Further, according to the present invention, it is possible to provide a parallel optical transmission device having a small skew between optical signals transmitted in parallel.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of a parallel optical transmission device according to the present invention.

FIG. 2 is an explanatory diagram of a transmitting side of the parallel optical transmission device of FIG. 1;

FIG. 3 is an explanatory diagram of a receiving side of the parallel optical transmission device of FIG. 1;

FIG. 4 is an explanatory diagram of light detection of the parallel optical transmission device of FIG. 1;

FIG. 5 is a sectional view of a parallel optical transmission module of the parallel optical transmission device of the present invention.

FIG. 6 is a sectional view of a parallel optical receiving module of the parallel optical transmission device of the present invention.

[Explanation of symbols]

Reference Signs List 10 laser array, 12, 14 laser, 20 lens array, 22, 24 lens, 30 prism array, 32, 34 triangle prism, 40 photodetector array, 41 to 48 photodetector, 50 ... optical fiber array,
52: entrance end, 54: exit end, 60: lens, 70: bright spot, 100: adder, 110, 112: circuit board, 12
0: data input terminal, 122: data output terminal, 20
0, 202: case, 210: ferrule, 212: ferrule receiver, 220, 222: male connector, 230,
232 female connector.

Claims (5)

[Claims] 1. An optical transmission module having two or more light sources, a modulation optical element for spatially modulating signal light from the light sources, and transmitting the signal light, and transmitting the signal light. And an optical fiber for converting the signal light from the optical fiber into a spatial frequency, and a light receiving module that receives the signal light and has two or more photodetectors. Optical transmission device. 2. The parallel optical transmission device according to claim 1, wherein the conversion optical element is a lens, and a distance between the lens and the photodetector is substantially a focal length of the lens. 3. The parallel optical transmission device according to claim 1, wherein the modulation optical element modulates the intensity distribution of the signal light so as to periodically change one-dimensionally or two-dimensionally. 4. An optical transmission module having two or more light sources and transmitting a signal light; an optical fiber having a plurality of cores for transmitting the signal light; and the signal from the optical fiber. A light receiving module having a conversion optical element for receiving light and converting the signal light into a spatial frequency, and two or more photodetectors, wherein the light transmission module is configured to output different signal light from the light source. Is incident on a plurality of the cores, wherein the optical receiving module separates the signal light transmitted through the same core by the conversion optical element, and is detected by the photodetector. 5. An optical fiber which transmits signal light from two or more light sources, has a plurality of cores, and a relative position between the cores is the same from a light input end to a light output end of the optical fiber. A parallel optical transmission method in which a signal light is incident and the signal light transmitted from the optical fiber is spatially Fourier transformed and detected.