JP2009093131A - Array type tap photodiode module and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost, compact, array type tap photodiode module for WDM transmission. <P>SOLUTION: Regarding the array type tap photodiode module, the fiber array of a plurality of pairs of input/output optical fibers adjacent to each other is formed at pitches capable of disregarding optical crosstalk. A method for centering the optical fiber array, the lens array 3 and a beam splitter bar 4 is optimized, and the parameter of the lens is optimized so that the beam may be smaller than the photodetecting diameter of a PD on the PD element surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an array-type tap photodiode module (hereinafter abbreviated as ATPDM) and a manufacturing method thereof. The present invention relates to a multi-channel ATPDM and a manufacturing method thereof.

  The rapid spread of the Internet has continued since 2000. The annual rate of increase is almost twice, and it is said that transmission capacity of about 1,000 times is required in the next 10 years. In order to cope with such an increase in traffic in the future, the wavelength channels of WDM transmission systems are being densified. In a high-density WDM or DWDM system, an optical waveguide type multiplexer / demultiplexer called AWG is used. In DWDM, an erbium-doped optical fiber amplifier (hereinafter abbreviated as EDFA) that amplifies multiple channels at once is used. An optical transmission system using an EDFA can be economically increased in capacity with a small number of repeaters using an existing optical cable, and is now widely used in trunk and submarine optical transmission systems. An EDFA generally has a wavelength characteristic of gain. If there is an irregularity in the signal power of each channel in WDM transmission, it is amplified by an amplifier and the irregularity is amplified. As a result, S / N is not uniform in the receiving unit, and a sufficient system margin cannot be secured. Therefore, an AWG that demultiplexes a WDM signal requires a number of devices that monitor the signal level of each wavelength channel after demultiplexing, that is, a number of tap PD (photodiode) modules.

In general, in order to monitor light in a transmission line, it is necessary to branch (referred to as a tap) a signal by a predetermined ratio.
Conventional tapping methods mainly use a type using a two-core ferrule, a lens, a splitter, and a photodiode. This is shown in FIG. FIG. 6 shows a two-core offset method in which a pair of input / output optical fibers are installed at positions symmetrical with respect to the center of the lens, and are branched into tap light and transmitted light by a beam splitter. Since the method of FIG. 6 can be made relatively small with an outer diameter of 3 mm to 5 mm, this type of tap PD module is currently used by the number of wavelength channels in the AWG and EDFA of the DWDM system.

  However, since the conventional tap PD module shown in FIG. 6 has an outer diameter of 3 mm to 5 mm, a space of 120 mm to 200 mm in width is required if it is stored as it is when the number of channels is 40. In addition, 80 input / output optical fibers together with AWGs and variable optical attenuators need to be stored and laid on the board, and the mounting cost cannot be ignored. In addition, waveguide type parts such as AWG can be reduced in size by increasing the difference in refractive index between the core and the clad. There was a problem.

  From the above background, an array-type tap photodiode module has long been desired. However, in the case of the array type, there are problems such as crosstalk due to light interference between channels in the module and the need to simultaneously couple multiple channels, and it has not been put into practical use so far.

  An object of the present invention is to solve the above-mentioned problems of the prior art and provide a small and low-cost array-type tap photodiode module for WDM transmission and a method for manufacturing the same.

  In order to achieve the above object, in the array-type tap photodiode module according to the present invention, a plurality of adjacent input / output optical fiber pairs are formed into a fiber array at a pitch at which optical crosstalk can be ignored. The lens array, the beam splitter, and the method of aligning and fixing the PD array are optimized, and the lens parameters are optimized so that the beam collimated by the lens array becomes smaller than the PD light receiving diameter on the PD element surface.

Hereinafter, the present invention will be described more specifically.
An array type tap photodiode module according to a first invention as an example of the present invention (hereinafter referred to as invention 1) is a pair of optical fibers arranged so that the distance between the clads of the two optical fibers is almost zero. With respect to the central axis of one lens of a lens array having n lenses, the exit end faces of a pair of optical fibers of an optical fiber array in which pairs are arranged at regular intervals with n pairs (n is an integer of 2 or more) The light emitted from the pair of first optical fibers is adjusted to a symmetrical position, collimated by the lens, branched into reflected light and transmitted light by a beam splitter bar having a predetermined reflectance, and the transmitted light is divided into n photo An array-type tap photodiode module characterized in that the reflected light is guided to one of the diode arrays and condensed by the lens onto a second optical fiber.

  An array-type tap photodiode module according to a second invention (hereinafter referred to as invention 2) in which the invention 1 is developed as an example of the present invention is collimated by a lens in the array-type tap photodiode module according to the invention 1. Array collimator parameters, that is, the distance between the optical fiber end face and the lens, the focal length of the lens, the effective diameter of the lens, and the light received from the lens so that the beam diameter of the transmitted light on the light receiving element is smaller than the effective light receiving diameter of the light receiving element. This is an array type tap photodiode module in which the relationship of the distance to the element is set.

  An array-type tap photodiode module manufacturing method according to a third invention (referred to as invention 3) obtained by developing the invention 1 as an example of the present invention is an optical fiber array in the array-type tap photodiode module according to the invention 1. After aligning the lens array and fabricating the array type fiber collimator, the position of the beam splitter is aligned three-dimensionally while monitoring the outputs of the n output optical fibers, and then n An array-type tap photodiode module manufacturing method characterized in that the position of a PD array is aligned so that n beams are coupled to each photodiode.

  An array-type tap photodiode module according to a fourth invention (referred to as invention 4) obtained by developing the invention 1 or 2 as an example of the present invention is an array-type tap photodiode array according to the invention 1 or 2, in which the adjacent one is 1 The array type tap photodiode array is characterized in that the arrangement direction of the pair of optical fibers is the same as the arrangement direction of the lens array and the photodiode array.

  An array-type tap photodiode module according to a fifth invention (referred to as invention 5) obtained by developing the invention 1 or 2 as an example of the present invention is the array-type tap photodiode module according to the invention 1 or 2, wherein the adjacent one 1 The array type tap photodiode module is characterized in that the arrangement direction of the pair of optical fibers is orthogonal to the arrangement direction of the lens array and the photodiode array.

  An array-type tap photodiode module according to a sixth invention (referred to as invention 6) obtained by developing the invention 1 or 2 as an example of the present invention is the array-type tap photodiode module according to the invention 1 or 2, wherein the adjacent one 1 The array type tap photodiode module is characterized in that the period of the pair of optical fibers is approximately 0.5 mm or more.

  An array type tap photodiode module according to a seventh invention (referred to as invention 7) as an example of the present invention has a pair of optical fibers arranged so that the distance between the clads of the two optical fibers is substantially zero. In an optical fiber array in which n pairs (n is an integer of 2 or more) are arranged at regular intervals, the distance between the center lines of two optical fibers constituting the optical fiber pair and the center of two adjacent optical fiber pairs This is an array-type tap photodiode module characterized in that the distance between the lines is different.

  As described above, the array-type tap photodiode module of the present invention is characterized by being small in size and low in cost. In particular, as the number of channels increases, the mounting cost per channel decreases. Further, since the tape fiber can be used when mounting in the AWG or EDFA, the mounting cost can be greatly reduced. As a result, if it is applied to a WDM transmission system using AWG or EDFA, it can contribute to long-distance / large-capacity transmission and economics of next-generation access systems.

Embodiments of a basic structure and manufacturing method of an array-type tap photodiode module as an example of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of an array-type tap photodiode module 20 as an example of the present invention. A 16-core optical fiber 1 in FIG. 1 is attached to an optical fiber array 2. The end face of the optical fiber array 2 is polished 8 degrees, and the end face is subjected to an AR coating for air.
A front view of the optical fiber array 2 viewed from the end face side of the optical fiber is shown in FIG. The optical fiber array 2 is fixed to the base 8 of the module. The relative position of the lens array 3 is aligned so that the beam array from the eight-core incident optical fibers of the optical fiber array 2 is directed in a predetermined direction. As a result, an array type collimator 9 is formed.
Thereafter, the lens array 3 is also fixed to the base 8 of the module. AR coating for air is also applied to both surfaces of the lens array 3.

  Next, the beam splitter bar 4 is aligned and fixed to the module base 8 so that the insertion loss is low and the variation is small while monitoring the output power of the eight-core outgoing optical fiber. Here, the beam splitter bar is a type having a transmittance of 10%. The insertion loss of the outgoing optical fiber with respect to the output of the incident optical fiber was 1.1 dB to 1.3 dB.

  Thereafter, the position of the PD array 5 is adjusted so that the 8-channel beam transmitted through the beam splitter is coupled to the 8-channel PD in the PD array 5 which has been die-bonded and wire-bonded to the PD mounting substrate 6 in advance. Fix to 8. Here, the PD mounting substrate 6 is a mold package with a lead frame, and the electrodes of the eight PDs are connected to predetermined terminals of the electrical terminals 7 arranged at a pitch of 1.27 mm. The PD array used in this example is a so-called electric crosstalk countermeasure type PD array in which a ring-shaped groove is provided around an electrode to suppress a beam leaking through an InP substrate layer inside the PD array.

  FIG. 2 shows a cross-sectional view of an optical fiber array and a lens used in an array type tap photodiode module as an example of the present invention. Reference numerals 1-1 to 1-16 denote optical fibers constituting the optical fiber array 2, and optical fibers 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, and 1-8, 1-9 and 1-10, 1-11 and 1-12, 1-13 and 1-14, and 1-15 and 1-16, respectively, have almost zero clad spacing between the two optical fibers. Alternatively, optical fiber pairs with a distance close to zero are formed, and each optical fiber pair is different from the distance between the center lines of the two optical fibers forming the optical fiber pair with a wider distance (pitch). Has been placed.

  A preferred embodiment will be described. As the optical fiber array 2, an optical fiber array 2 in which two pairs of optical fiber pairs adjacent to each other at a pitch of 127 μm were arrayed at a pitch of 500 μm was used. The optical fibers 1-1 and 1-2 constituting one optical fiber pair have a distance between center lines of 127 μm, and the optical fibers 1-3 and 1-4 constituting one adjacent optical fiber pair are also included. Each centerline distance is 127 μm to form a pair, and optical fibers 1-5 and 1-6 constituting the next pair of optical fibers are also paired with each centerline distance being 127 μm. As described above, a pair of optical fibers constituting each pair of optical fiber pairs are arranged adjacent to each other at a pitch of 127 μm. Then, the center line 10-1 of the lens 3-1 and the center of the adjacent optical fiber pairs 1-3, 1-4 are located at the same positions as the center lines of the optical fiber pairs 1-1, 1-2 constituting the pair. The distance between the center line 10-2 of the lens 3-2 that is at the same position as the line is 500 μm, and the center line 10 of the lens 3-2 that is at the same position as the center line of the optical fiber pairs 1-3 and 1-4 -2 and the center line 10-3 of the lens 3-3 at the same position as the center line of the adjacent optical fiber pairs 1-5 and 1-6, the distance between the center of each optical fiber pair is 500 μm. Each optical fiber pair is arranged so that the distance between the lines and the distance between the center lines 10-1 to 10-8 of the lenses 3-1 to 3-8 are 500 μm. The pitch of each lens 3-1 to 3-8 of the lens array is 500 μm. Thus, the optical fiber array is of unequal pitch type.

FIG. 3 shows a cross-sectional view when the equal pitch optical fiber array 2a and the lens array 3a are used. Optical fibers 1-21 and 1-22, 1-23 and 1-24,... 1-35 and 1-36 each constitute an optical fiber pair, and each optical fiber pair has a lens 3 as shown in the figure. -11, 3-12, ... 3-18.
In this case, the lens pitch is 0.25 mm. Although the present structure was implemented before the present invention, the result was that optical crosstalk in which light from other channels leaked into PDs arranged at a pitch of 0.25 mm could be only about −25 dB. In this experiment, optical crosstalk to PDs separated by 0.5 mm or more is not recognized. Therefore, in the array-type tap photodiode module in the embodiment of the present invention, the pitch of the lens array and PD array is set to 0. 0. It was 5 mm. The light receiving diameter of the PD was set to 80 μm in consideration of dark current.
As a result of the experiment, a good value of crosstalk −40 dB was obtained.

  FIG. 4 shows a front view of the optical fiber array 2 used in the present invention. As shown in FIG. 4, the optical fiber array 2 described with reference to FIG. 2 has a glass V-groove block 12 holding optical fibers 1-1 to 1-16 in each V-groove and a substrate 13 disposed so as to oppose it. is doing. Each of the optical fibers 1-1 to 1-16 is housed one by one in each of the V-grooves 12-1 to 12-16 formed in the V-groove block 12, and is formed by the V-groove block 12 and the substrate 13 disposed opposite thereto. It is clamped, the position of each optical fiber is confirmed, and it fixes with the adhesive agent which is not shown in figure.

  Each optical fiber is held, positioned and fixed in a three-point support state by the two sides of the V-groove accommodated therein and the substrate 13 in contact with the optical fiber.

  4 is an unequal pitch type in which the distance between the center lines of each of the two optical fibers constituting each optical fiber pair is different from the distance between the center lines of adjacent optical fiber pairs. It is a fiber array.

The specifications of the lenses used in the examples of the present invention are as follows.
Material: Silicon Lens outer diameter: 0.36mm
Effective lens diameter: 0.29mm
Focal length: 0.32mm
Array pitch: 0.5 ± 0.0005mm
Substrate thickness: 1mm
As a result, the outer diameter of the collimated beam is approximately 60 μm, and a condensing lens array for the PD used in the current tap module becomes unnecessary. As a result, material costs could be reduced.

  FIG. 5 shows a front view of an optical fiber array 2b as another example used in the array-type tap photodiode module of the present invention. In the optical fiber array 2b, a glass V-groove block 12a having V-grooves 12a-1 to 12a-8 that can hold one optical fiber and a V-groove 12b-1 that can hold one optical fiber. -12b-8 glass V-groove block 12b, V-grooves 12a-1, 12b-1, 12a-2, 12b-2, 12a-3, 12b-3, ... 12a-8, 12b -8 is opposed to each other, and the two optical fibers of the optical fiber pair are arranged so as to be in close contact with each other in the two V-grooves facing each other in the apex direction of the opposed V-grooves. As can be seen, optical fibers 1-42 and 1-41 are provided in the V grooves 12a-1 and 12b-1, and optical fibers 1-44 and 1-43 are provided in the V grooves 12a-2 and 12b-2. The optical fibers 1-46 and 1-45 are in close contact with the V grooves 12a-3 and 12b-3, and the optical fibers 1-46 and 1-45 are in close contact with the V grooves 12a-8 and 12b-8, respectively. Is held.

  In this case, the distance between the optical fibers inevitably becomes the outer diameter of the optical fiber. The optical fiber array 2b in FIG. 5 has the merit that the optical crosstalk can be reduced because the reflection direction of the incident beam in the beam splitter is orthogonal to the direction of the PD array, but the upper and lower stages are lower than the optical fiber array 2 shown in FIG. However, since the number of alignment man-hours for each of the eight-core optical fiber arrays increases, there is a problem that the cost increases.

  In the assembly of the array type tap photodiode module of the present invention, the optical fiber array, the lens array, and the beam splitter are fixed to the module base 8 after alignment. . Depending on the required reliability, either method can be selected. In the embodiment of the array type tap photodiode module of the present invention, a plastic cover was put on the base of the module and sealed with an epoxy resin.

  Although the embodiment of the present invention has been described with reference to the drawings, the present invention is not limited to this, and many variations can be made based on the technical idea of the present invention apparent from the above description. It is what. For example, the optical fiber can be held using a concave portion or a hole obtained by taking a part of the V groove instead of the V groove holding the optical fiber.

  As described above, the array-type tap photodiode module of the present invention is small in size and low in cost. In particular, as the number of channels increases, the mounting cost per channel decreases, and long-distance / large-capacity transmission and next-generation access systems. It can also be used widely in optical communications, such as contributing to the economics of

  1 is an overall configuration diagram of an array-type tap photodiode module of the present invention.   It is sectional drawing of the unequal pitch optical fiber array and lens of this invention.   It is sectional drawing explaining an equal pitch optical fiber array and a lens.   It is a front view of the Example of the unequal pitch optical fiber array of this invention.   It is a front view of another Example of the unequal pitch optical fiber array of this invention.   It is a block diagram of the conventional tap module for single channels.

Explanation of symbols

1, 1-1 to 1-16, 1-21 to 1-36, 1-41 to 1-56, 1a, 1b: optical fiber 2: optical fiber array 3: lens array 3-1 to 3-8, 3 -11 to 3-18: Lens 4: Beam splitter bar 5: PD array 6: PD mounting substrate 7: Electrical wiring 8: Module base 9: Optical fiber array collimator 10-1 to 10-8: Lens center line 11- 1-11-16: Core center of optical fiber 12: Glass V groove block 12a-1 to 12a-8, 12b-1 to 12b-8: V groove 13: Cover of V groove block 14: 2-core ferrule 15- 1, 15-2: Lens 16: Beam splitter 17: Photodiode

Claims (7)

  A pair of optical fiber arrays in which a pair of optical fiber pairs arranged so that the distance between the clads of the two optical fibers is almost zero is arranged at a constant interval (n is an integer of 2 or more). The exit end face of the optical fiber is adjusted to a position symmetrical to each other with respect to the central axis of one lens of the lens array having n lenses, and the light emitted from the pair of first optical fibers is collimated by the lens and predetermined. The beam splitter having a reflectivity of 1 is divided into reflected light and transmitted light, the transmitted light is guided to one of n photodiode arrays, and the reflected light is condensed on the second optical fiber by the lens. Array type tap photodiode module.   2. The array-type tap photodiode module according to claim 1, wherein the parameters of the array collimator, that is, the optical fiber are set so that the diameter of the beam on the light receiving element of the transmitted light collimated by the lens is smaller than the effective light receiving diameter of the light receiving element. An array-type tap photodiode module that sets the relationship between the distance between the end face and the lens, the focal length of the lens, the effective diameter of the lens, and the distance from the lens to the light receiving element.   2. The array-type tap photodiode module according to claim 1, wherein the position of the optical fiber array and the lens array is adjusted in advance to manufacture an array-type fiber collimator, and then the beam splitter is monitored while monitoring the outputs of the n output optical fibers. The array type tap photodiode is characterized in that the position of the PD array is fixed after being three-dimensionally aligned, and then the position of the PD array is aligned so that n beams are coupled to the n photodiodes. Module manufacturing method.   3. The array-type tap photodiode array according to claim 1, wherein an arrangement direction of a pair of adjacent optical fibers is the same as an arrangement direction of the lens array and the photodiode array. array.   3. The array type tap photodiode module according to claim 1, wherein an arrangement direction of a pair of adjacent optical fibers is orthogonal to an arrangement direction of the lens array and the photodiode array. .   3. The array-type tap photodiode module according to claim 1, wherein a period of a pair of adjacent optical fibers is approximately 0.5 mm or more.   In an optical fiber array in which a pair of optical fiber pairs arranged so that the interval between the clads of two optical fibers is almost zero is arranged at a constant interval, n pairs (n is an integer of 2 or more), an optical fiber An array-type tap photodiode module, wherein a distance between center lines of two optical fibers constituting a pair is different from a distance between center lines of two adjacent optical fiber pairs.

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