JP7091600B2 - Optical receiver module - Google Patents

Description

The present invention relates to an optical receiving module, and more particularly to an optical receiving module that receives multiplexed wavelength-multiplexed signal light in which a plurality of signal lights having different wavelengths from each other and outputs an electric signal corresponding to each signal light.

In recent years, communication speeds have been increasing, and optical receiving modules used in optical transceivers and the like are required to support transmission speeds of 40 Gbps and 100 Gbps. In such high-speed transmission, wavelength-multiplexed signal light in which a plurality of signal lights having different wavelengths are multiplexed is often used instead of signal light having a single wavelength.

When receiving wavelength division multiplexing signal light, if the optical transceiver is provided with a plurality of optical receiving modules equipped with only one light receiving element, the optical transceiver becomes large. Therefore, in a small optical transceiver, a single light receiving element is used. It is mounted on the optical receiving module of the above, and the wavelength division multiplexing signal light is received by the optical receiving module.

As an optical receiving module that receives wavelength division multiplexing signal light, for example, there is one disclosed in Patent Document 1. This optical receiving module includes a light emitting section that emits light having a plurality of wavelengths from the emitting end of an optical fiber having a finite diameter, a converging lens section that converges the light emitted from the emitting end of the light emitting section, and a converging lens section. Arranged between the light reflecting unit, the plurality of wavelengths are divided into two, one of the divided light is incident on the first wavelength separator, and the other light is incident on the second wavelength separator. A light demultiplexing unit to be incident, a condensing lens unit that condenses each light demultiplexed by the first and second wavelength separation units, and a plurality of light receiving light condensing by the condensing lens. It is equipped with a light receiving element.

Japanese Unexamined Patent Publication No. 2009-198958

The optical receiving module disclosed in Patent Document 1 divides 8-channel input signal light into 4 channels of signal light on the short wavelength side and 4 channels on the long wavelength side by an input WSF (Wavelength Selective Filter). Wavelengths are separated by a 4-channel optical demultiplexer (also referred to as Optical De-Multiplexer: O-DeMux) placed at equal distances from the input WSF. However, the installation angle of the input WSF with respect to the input signal light is set to a large angle. That is, the input WSF is arranged so that the optical axis of the reflected light is approximately 90 ° with respect to the optical axis of the input signal light and the incident angle is approximately 45 ° with respect to the input signal light.

By the way, the wavelength separation characteristic of WSF (the steepness of the filter) largely depends on the incident angle of light. The WSF generally compensates for its wavelength segregation characteristics for optical signals with an incident angle of 0 °. This is because the WSF is composed of a dielectric multilayer film, and the wavelength separation characteristic gradually deteriorates as the incident angle increases. Further, in order to improve the steepness of the filter, it is necessary to increase the number of dielectric multilayer films constituting the filter. However, when the number of films increases, the light transmittance decreases and the WSF itself. Will be expensive.

For example, in the CWDM (Coarse Wavelength Division Multiplexing) standard that defines a wavelength interval of 20 nm, if the incident angle is not set within 20 °, preferably within 15 °, light in a wavelength band adjacent to one wavelength band separated by WSF will also be emitted. Will be included. For example, in the optical receiving module disclosed in Patent Document 1, which separates an optical signal of 8 channels into 4 channels (0 to 3 channels) on the short wavelength side and 4 channels (4 to 7 channels) on the long wavelength side, the optical signal on the short wavelength side A part of the optical signal of the 4th channel existing on the shortest wavelength side on the long wavelength side is a part of the optical signal of the 3rd channel existing on the longest wavelength side on the short wavelength side in the optical signal on the long wavelength side. Will be included.

Further, since the optical output end of the optical fiber is not regarded as a point light source but a light source having a finite spread, the output light of the convergent lens portion is not completely collimated light. Since the optical path lengths of the signal lights of each wavelength are different, the beam diameter of the output light of each convergent lens unit is different, so that the light condensing degree to each light receiving element is different and a difference in optical coupling efficiency is generated. It is possible to compensate for the difference in optical coupling efficiency between channels by aligning each condensing lens and light receiving element separately for each channel without forming an array, but it reduces production efficiency. Will be accompanied.

It is preferable that the light receiving elements that receive the signal light of each of the eight channels are arranged in a row on the side opposite to the light incident side of the optical demultiplexer with the optical demultiplexer interposed therebetween. An electric circuit can be used when an IC (integrated circuit) with an integrated 8-channel preamplifier is used, when two preamplifier ICs with a 4-channel + 4-channel configuration are used, or when a preamplifier IC is provided for each channel individually. It is desirable that the parts are mounted separately from the optical component mounting parts.

The present invention has been made in view of these circumstances, and is an optical receiving module that receives wavelength division multiplexing signal light, has good wavelength separation characteristics, and does not reduce production efficiency for each wavelength of signal light. It is possible to reduce the difference in optical coupling efficiency, and it is an object of the present invention to provide an optical receiving module in which an electric circuit unit can be mounted together.

The optical receiving module according to one aspect of the present invention receives wavelength-multiplexed signal light in which a plurality of signal lights having different wavelengths are multiplexed via an optical fiber, and a plurality of signals included in each of the signal lights. A first lens that uses the wavelength-multiplexed signal light as input light and outputs convergent light, and an incident angle of 20 ° or less with respect to the optical axis of the convergent light. An input wavelength selection filter that divides the convergent light into transmitted light and reflected light containing a predetermined wavelength multiplex signal light, and the transmitted light to each of the signal lights according to the wavelength of the signal light contained in the transmitted light. The first optical demultiplexer to be separated, the second optical demultiplexer to separate the reflected light into the signal light according to the wavelength of the signal light contained in the reflected light, and the first and second optical demultiplexers. A plurality of second lenses that collect the signal light separated by the optical demultiplexer, a prism mirror that reflects the convergent light output from the first lens, and the transmission from the input wavelength selection filter. A mirror that reflects light is provided, and the distance from the wavelength multiplex signal light emitting end of the optical fiber to the first lens is longer than the focal distance on the optical fiber side of the first lens, and the first lens is provided. At the distance between the shortest optical path length and the longest optical path length from the first lens to the second lens, the beam waist of convergent light, which is a quasi-colimated light having a beam waist output by the first lens, is arranged. The input wavelength selection filter divides the convergent light reflected by the prism mirror into the transmitted light and the reflected light, and the transmitted light is reflected by the mirror and input to the first optical demultiplexer. The reflected light is reflected again by the prism mirror and input to the second optical demultiplexer, and the optical path length from the first lens to the light incident end of the first optical demultiplexer and the first The optical path lengths from the lens to the light incident end of the second optical demultiplexer are equal, and the optical axis of the input light of the first optical demultiplexer and the optical axis of the input light of the second optical demultiplexer are parallel to each other. Moreover, the optical axes of the signal lights separated by the first optical demultiplexer and the second optical demultiplexer are all parallel to each other.

According to the present invention, it is an optical receiving module that receives wavelength division multiplexing signal light, has good wavelength separation characteristics, and can reduce the difference in optical coupling efficiency for each wavelength of signal light without lowering production efficiency. It is possible, and the electric circuit unit can be mounted together.

It is a figure which shows schematically the optical receiving module which becomes the reference example of this invention. It is a figure which shows the state of the light output from the optical output end of an optical fiber in a conventional optical module. It is a figure which shows the relationship between the optical path length and the beam diameter at the time of using the collimating lens which can obtain various beam diameters at the focal position of a lens. It is a figure which shows the behavior of the light output from the optical output end of an optical fiber in the optical module which concerns on one aspect of this invention. It is a figure which shows the relationship between the beam diameter and the beam waist of the light receiving module which concerns on one aspect of this invention. It is a figure which shows schematically the optical receiving module which concerns on one aspect of this invention . It is a perspective view of the optical receiving module shown in FIG.

Hereinafter, a preferred embodiment of the optical receiving module of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to these examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. Further, in the following description, the description may be omitted because the configurations with the same reference numerals are the same in different drawings.

FIG. 1 is a diagram schematically showing an optical receiving module as a reference example of the present invention. The optical receiving module 10 receives a wavelength-multiplexed signal light in which a plurality of signal lights having different wavelengths (λ0 to λ7) are multiplexed, and outputs an electric signal corresponding to each signal light. The optical receiving module 10 includes a receptacle for engaging an external optical fiber in a single mode, a package for accommodating a light receiving element, an optical component, and the like, and a terminal portion for electrical connection with an external circuit.

A sleeve for receiving the ferrule attached to the tip of the external optical fiber is provided in the receptacle, and the external optical fiber is optically coupled to the coupling fiber (single mode fiber) 11a of the stub 11 arranged in the sleeve. do. The receptacle contains a first lens 12 that converts an optical signal emitted from the output end of the coupled fiber 11a into quasi-colimated light. The first lens 12 is a collimated lens that outputs collimated light when the distance from the light output end of the coupled fiber 11a to the first lens 12 and the focal length of the first lens 12 are matched.

However, as will be described later, the first lens 12 is not used in a state where the distance between the optical output end of the coupled fiber 11a and the first lens 12 and the focal length of the first lens 12 are matched. , The distance from the output end of the coupled fiber 11a to the first lens 12 is longer than the focal length of the first lens 12. As a result, the output light of the first lens 12 becomes convergent light. The output light of the first lens 12 is guided into the package through an optical window (not shown).

The package is an input wavelength selection filter (hereinafter referred to as "input WSF") that divides the convergent light emitted by the first lens 12 into transmitted light including wavelength-multiplexed signal light composed of signal light having a predetermined wavelength and reflected light. .) 13 is installed. Specifically, the input WSF 13 transmits the signal light (wavelengths λ ₁ to λ ₄ ) of the short wavelength side 4 channels (channels 0 to 3), and the signal light of the long wavelength side 4 channels (channels 4 to 7). (Wavelength λ ₅ to λ ₈ ) is reflected. The channel is used synonymously with the lane shown in FIG. The input WSF 13 is arranged at an angle of incidence within 20 °, preferably within 15 °, with respect to the focused light emitted by the first lens 12. As a result, deterioration of the wavelength separation characteristic of the input WSF 13 is suppressed, and the signal lights of the short wavelength side 4 channels and the long wavelength side 4 channels do not mix with each other.

The transmitted signal light (wavelengths λ ₁ to λ ₄ ) transmitted through the input WSF 13 is directly incident on the first optical demultiplexer (hereinafter referred to as “O—DeMax”) 21. Further, the reflected signal light (wavelengths λ ₅ to λ ₈ ) reflected by the input WSF 13 is converted into a second O- after the optical axis thereof is converted in parallel with the optical axis of the transmitted signal light by the mirror 14 and the mirror 15. It is incident on DeMax22. The first O-DeMax 21 integrates one input port 21a, a number of wavelength selection filters 21b and output ports 21c according to the number of wavelength multiplexes, and a reflective film 21d, and similarly, a second O-DeMax 21. The O-DeMax 22 integrates one input port 22a, a number of wavelength selection filters 22b and output ports 22c according to the number of wavelength multiplexes, and a reflective film 22d. In this embodiment, the first O-DeMax 21 and the second O-DeMax 22 are arranged in parallel. And, such an arrangement makes it possible to mount an electric circuit part such as a light receiving element and a preamplifier circuit for amplifying a signal from a light receiving element, which will be described later, collectively on one side of the optical receiving module 10.

When wavelength multiplex signal light including signal light having a plurality of different wavelengths (λ ₁ to λ ₄ ) transmitted through the input WSF 13 is input to the input port 21a of the first O-DeMax 21, the first wavelength selection filter 21b is used. , Only the signal light of the first wavelength λ ₁ is transmitted from the output port 21c, and the signal light of other wavelengths (λ ₂ , λ ₃ , λ ₄ ) is reflected. This reflected signal light is totally reflected by the reflection film 21d provided on the surface facing the surface provided with the wavelength selection filter 21b (the surface on which the input port 21a is formed), and is incident on the second wavelength selection filter 21b. .. The signal light incident on the second wavelength selection filter 21b is transmitted by the wavelength selection filter 21b only to the signal light of the second wavelength λ ₂ , and the signal light of the second wavelength λ ₂ is transmitted to the output port 21c. On the other hand, signal lights of other wavelengths (λ ₃ , λ ₄ ) are reflected and head toward the reflective film 21d again. Hereinafter, transmission and reflection are repeated in the same manner, and only signal light having one wavelength is output from each of the output ports 21c. The signal light output from the output port 21c passes through the second lens 31a of the lens array 31 and is received by the PD 41a of the PD (Photo Diode) array 41.

The wavelength multiplex signal light including the signal lights of a plurality of wavelengths (λ ₅ to λ ₈ ) different from each other reflecting the input WSF 13 is input to the input port 22a of the second O-DeMax 22 and is the same as the first O-DeMax 21. In addition, it is separated by the second O-DeMax22, and only the signal light having one wavelength is output from each of the output ports 22c. The plurality of signal lights output by the output port 22c pass through the second lens 32a of the lens array 32 and are received by the PD 42a of the PD array 42. The second lens 31a and the second lens 32a are condenser lenses, and PD41a and PD42a are examples of the "light receiving element" of the present invention. The second lenses 31a, 32a and PD41a, 42a may be integrated for each of the first and second O-DeMax21, 22 respectively. The integration makes it possible to reduce the size of the optical receiving module.

As described above, the signal light transmitted through the input WSF 13 and the reflected signal light are physically separated into signal lights for each channel by the first O-DeMax 21 and the second O-DeMax 22, respectively. However, as is clear from the optical system shown in FIG. 1, the optical path length from the first lens 12 to the first O-DeMax21 and the second O-DeMax22 is the optical path length for the second O-DeMax22. Is longer than the optical path length of the first O-DeMax21 by the distance required for translation of its optical axis. Further, the optical path lengths from the input ports 21a and 22a of the first O-DeMax 21 and the second O-DeMax 22 to the output ports 21c and 22c are also different in each lane (channel). In the optical system shown in FIG. 1, the optical path length from the first lens 12 to the second lenses 31a and 32a is the shortest in the lane 0 and the longest in the lane 7.

Since the optical path length differs between the lanes in this way, in the conventional optical module, the focal point of the first lens 12 and the optical output end of the coupled fiber 11a are matched, and the first lens 12 functions as a so-called collimating lens. At the same time, by using the second lenses 31a and 32a as a condenser lens, the difference in the distance between the lanes between the first lens 12 and the second lenses 31a and 32a was compensated.

However, the optical output end of the coupled fiber 11a is ideal for the output light from the first lens 12 to be a perfect collimated light by matching the focal point of the first lens 12 with the optical output end of the coupled fiber 11a. Only when it can be regarded as a typical point light source. In reality, the light output end has a finite spread.

FIG. 2 is a diagram showing a state of light output from an actual optical output end of a coupled fiber 11a in a conventional optical module. As described above, the optical output end of the actual coupled fiber 11a is regarded as a light source having a finite spread, and the distance L1 from such an optical output end to the first lens 12 and the focal length of the first lens 12 When arranged in line with Lf, as shown in the figure, the output light from the first lens 12 obtains a field pattern close to the collimated light in the vicinity of the first lens 12. However, as the distance from the first lens 12 increases, only a diffused field pattern can be obtained. That is, in lane 0 having a short optical path length, a field pattern close to collimated light can be obtained, but in lane 7 or the like having a long optical path length, only a diffused field pattern can be obtained.

FIG. 3 is a diagram showing the relationship between the optical path length and the beam diameter when a collimating lens that can obtain various beam diameters at the focal position of the lens is used, and is 200 to 200 at the position of the focal distance of the first lens 12. When a collimated lens capable of obtaining a beam diameter of 500 μm is adopted, the beam diameter at a point distant from the focal distance by a distance corresponding to the horizontal axis is estimated by assuming a Gaussian beam for the light source. For example, for 200 μm, the focal point is the position on the horizontal axis of 0 mm, and although a beam diameter of 200 μm can be obtained there, the diameter increases as the distance increases. For 500 μm, 0 mm is the focal point, and the spread of the beam is suppressed even if the distance is increased. From this behavior, if the beam diameter is increased, the spread can be suppressed. However, in order to obtain light with a large beam diameter, it is necessary to increase the focal length of the lens and increase the lens diameter. Further, the O-DeMax and the condenser lens also need to be increased in size in order to cope with light having a large beam diameter, which leads to an increase in size and cost of the entire optical receiving module.

Then, in the actual optical system, particularly, in the first O-DeMax21 and the second O-DeMax22, four wavelength selection filters- (WSF) 21b and 22b are arranged in close proximity to each other, and interfere with the adjacent WSF. In order to avoid this, it is necessary to set the beam diameter of the incident light to 300 μm or less. In FIG. 3, Ln shows an approximation of the distance from the focal point of the first lens 12 to the second lens 31a or 32a as the optical path length to the MLA (Micro Lens Array) position for each lane. There is an optical path difference of about 10 mm for the equivalent lanes (for example, L0 and L4, L1 and L5) between the O-DeMax 21 and the second O-DeMax 22. As described above, under the condition of the initial beam diameter of 300 μm, the beam diameter increases monotonically with respect to the distance, and therefore, the rule of 300 μm is not satisfied in any of the lanes.

Therefore, in the present embodiment, the optical output end of the coupled fiber 11a and the first lens 12 are arranged in an optical system in which two first and second O-DeMax (4 channels each) 21 and 22 are arranged in parallel. Adjust and position the beam waist between the distance of the shortest optical path length from the first lens 12 to the second lenses 31a, 32a and the distance of the farthest optical path length.

FIG. 4 shows the behavior of the light output from the optical output end of the optical fiber in the optical module according to one aspect of the present invention. In the optical receiving module 10, the distance L from the optical output end of the coupled fiber 11a to the first lens 12 is made larger than the focal length Lf of the first lens 12, and the output light of the first lens 12 is not collimated light. It is converted to quasi-colimated light.

Here, since the distance L from the optical output end of the coupled fiber 11a to the first lens 12 is larger than the focal length Lf of the first lens 12, the output light from the first lens 12 becomes convergent light. As shown in FIG. 4, the beam waist position is set to the distance between the lane 0 (L0) having the shortest optical path length and the lane 7 (L7) having the longest optical path length. More specifically, in the present embodiment, the distance between the optical path length distance (L0) of lane 1 and the optical path length distance (L2) of lane 2, or the optical path length distance (L4) of lane 4 and the lane. It is set to the distance between the optical path length of 5 and the distance (L5). As a result, in the light receiving module 10, the difference between the lanes having the beam diameters projected on the second lenses 31a and 32a becomes very small.

FIG. 5 is a diagram showing the relationship between the beam diameter and the beam waist of the optical receiving module according to one aspect of the present invention. As shown in FIG. 5, since the signal light emitted from the first lens 12 is not collimated light but convergent light, the distance (L0) to the second lens 31a having the shortest optical path length and the farthest second lens 31a. There is a beam waist in the middle of the distance (L7) to the lens 42a. Further, the beam diameter of the signal light in the second lens 31a having the shortest optical path length (L0) from the first lens and the beam diameter of the signal light in the second lens 32a having the longest optical path length (L7) are predetermined. The size can be within 300 μm, which is the size. Thereby, in all the lanes, the beam diameter in the second lenses 31a and 32a can be set to a size within 300 μm, which is a predetermined size.

In the above embodiment, there is an optical path difference of about 10 mm for the equivalent lane between the first O-DeMax 21 and the second O-DeMax 22. However, after the transmitted signal light transmitted through the input WSF 13 is further reflected by two reflection mirrors, it is input to the first O-DeMax 21 and the optical path length from the input WSF 13 to the input port 21a of the first O-DeMax 21 is input. The optical path length from the WSF 13 to the input port 22a of the second O-DeMax 22 may be equal. As a result, the optical path length from the first lens 12 to the input port 21a of the first O-DeMax 21 and the optical path length from the first lens 12 to the input port 22a of the second O-DeMax 22 become equal and coupled. Since the distance L from the optical output end of the fiber 11a to the first lens 12 can be adjusted in the same manner as when one O-DeMax is used, the adjustment work can be reduced.

FIG. 6 is a diagram schematically showing an optical receiving module according to an aspect of the present invention, and FIG. 7 is a perspective view of the optical receiving module shown in FIG. The optical receiving modules shown in FIGS. 6 and 7 are optical receiving modules for 8-wave multiplex light, and have an optical path length from the first lens 12 to the input port of the first O-DeMax and the first lens 12 to the first. It shows an example which made the optical path length to the input port of 2 O-DeMax equal. In FIGS. 6 and 7, the optical fiber, the second lens (lens array), and the light receiving element (PD array) are omitted.

The package of the optical receiving module includes a prism mirror 16, an input WSF 17, a mirror 18, a first O-DeMax23, a second O-DeMax24, and a mirror 25. The prism mirror 16 has an isosceles triangle shape in which the apex angle θ of the cross section is larger than 90 °. Make it incident. The input WSF 17 transmits signal light of 4 channels on the short wavelength side (wavelengths λ ₁ to λ ₄ ) and reflects signal light of 4 channels on the long wavelength side (wavelengths λ ₅ to λ ₈ ). The bottom of the prism mirror 16 and the incident surface of the input WSF 17 are arranged so as to be substantially parallel to the optical axis of the first lens 12, and the apex angle θ of the prism mirror 16 is such that the incident angle of the focused light of the input WSF 17 is set to be substantially parallel. The angle is set to be within 20 °, preferably within 15 °.

The transmitted signal light (wavelengths λ ₁ to λ ₄ ) transmitted through the input WSF 17 is converted by the mirror 18 so that its optical axis is parallel to the optical axis of the first lens 12, and then the first O-DeMax 23. Incident to. Further, the reflected signal light (wavelengths λ ₅ to λ ₈ ) reflected by the input WSF 17 is reflected again on the other equal side of the prism mirror 16 and converted so that its optical axis is parallel to the optical axis of the first lens 12. After that, it is incident on the second O-DeMax22. As a result, the optical axis of the transmitted signal light (wavelength λ ₁ to λ ₄ ) on the short wavelength side incident on the first O-DeMax 23 and the reflected signal light (wavelength λ) on the long wavelength side incident on the second O-DeMax 24. The optical axis of ₅ to λ ₈ ) becomes parallel.

Further, the optical axis of the transmitted signal light (wavelength λ ₁ to λ ₄ ) on the short wavelength side incident on the first O-DeMax 23 and the transmitted signal light (wavelength λ ₅ ) on the long wavelength side incident on the second O-DeMax 24. By moving the prism mirror 16 in the vertical direction of the paper surface of FIG. 6 while keeping it parallel to the optical axis of ~ λ ₈ ), the optical path from the input WSF 17 to the light incident end of the first O-DeMax 23. It is possible to change the length. Thereby, the optical path length from the first lens 12 to the light incident end of the first O-DeMax is made equal to the optical path length from the first lens to the light incident end of the second O-DeMax. Since the distance L from the optical output end of the coupled fiber (not shown) to the first lens 12 can be adjusted in the same manner as when one O-DeMax is used, the adjustment work can be reduced.

The first O-DeMax 23 integrates one input port 23a, a number of wavelength selection filters 23b and output ports 23c according to the number of wavelength division multiplexing, and a reflection film 23d, and is the first O-DeMax 23 shown in FIG. It has the same configuration and function as the O-DeMax21 of. Similarly, the second O-DeMax 24 integrates one input port 24a, a number of wavelength selection filters 24b and output ports 24c according to the number of wavelength division multiplexing, and a reflection film 24d. It has the same configuration and function as the second O-DeMax22 shown in 1.

In the present embodiment, the first O-DeMax23 and the second O-DeMax24 are arranged in a C shape. The input port 23a of the first O-DeMax 23 and the input port 24a of the second O-DeMax 24 are arranged so as to be located outside the package. Therefore, the signal light separated and output by the first O-DeMax 23 and the signal light separated and output by the second O-DeMax 24 have the longest wavelength of λ ₅ and the shortest wavelength of λ ₁ . The wavelength selection filters 23b and 24b are arranged so as to be aligned. By arranging the first O-DeMax 23 and the second O-DeMax 24 in a V shape in this way, the optical path length from the first lens 12 to the light incident end of the first O-DeMax and the first O-DeMax are described. The package can be miniaturized while setting the optical path length from the lens 1 to the light incident end of the second O-DeMax equally.

Instead of arranging the input port 23a of the first O-DeMax 23 and the input port 24a of the second O-DeMax 24 so as to be located outside the package, the input port 23a of the first O-DeMax 23 is the first. It may be arranged so as to be located on the same side as the input port 24a of the O-DeMax 24 of 2, and the first O-DeMax 23 and the second O-DeMax 24 may be arranged in parallel.

In the present embodiment, the signal light (wavelengths λ ₁ to λ ₄ ) separated and output by the first O-DeMax 23 and the signal light (wavelengths λ ₅ to λ ₈ ) separated and output by the second O-DeMax 24). As shown in FIG. 7, the mirror 25 changes each optical axis by 90 ° from the horizontal direction to the vertical direction. As the mirror 25, a prism mirror having a right-angled isosceles triangle can be used. Then, the signal light whose optical axis is changed in the vertical direction by the lens array, which is a second lens (not shown), is collected and output to a PD array having a light receiving element (not shown). In this way, by changing the optical axis of the signal light from the first O-DeMax23 and the second O-DeMax24 by 90 ° in the vertical direction, it is connected to the rear stage of the lens array, the PD array, and the PD array. Circuit components such as a preamplifier for optical reception can be arranged three-dimensionally, and the package can be miniaturized.

10 ... Optical receiving module, 11 ... Stub, 11a ... Coupled fiber, 12 ... First lens, 13, 17 ... WSF, 14, 15, 18, 25 ... Mirror, 16 ... Prism mirror, 21, 23 ... First O-DeMax, 21a, 22a, 23a, 24a ... Input port, 21b, 22b, 23b, 24b ... Wavelength selection filter, 21c, 22c, 23c, 24c ... Output port, 21d, 22d, 23d, 24d ... Reflective film, 22 , 24 ... 2nd O-DeMax, 31, 32 ... lens array, 31a, 32a ... second lens, 41, 42 ... PD array, 41a, 42a ... PD.

Claims (7)

An optical receiving module that receives wavelength division multiplexing signal light in which a plurality of signal lights having different wavelengths are multiplexed via an optical fiber and extracts a plurality of signals contained in each of the signal lights.
A first lens that uses the wavelength division multiplexing signal light as input light and outputs convergent light,
An input wavelength selection filter that is arranged at an incident angle of 20 ° or less with respect to the optical axis of the convergent light and divides the convergent light into transmitted light and reflected light, each including a predetermined wavelength multiplex signal light.
A first optical demultiplexer that separates the transmitted light into each of the signal lights according to the wavelength of the signal light contained in the transmitted light.
A second optical demultiplexer that separates the reflected light into each of the signal lights according to the wavelength of the signal light contained in the reflected light.
A plurality of second lenses that collect the signal light separated by the first and second optical demultiplexers, and a plurality of second lenses.
A prism mirror that reflects the convergent light output from the first lens, and
A mirror that reflects the transmitted light from the input wavelength selection filter.
The distance from the wavelength division multiplexing signal light emitting end of the optical fiber to the first lens is longer than the focal length on the optical fiber side of the first lens.
The beam waist of convergent light, which is a quasi-colimated light having a beam waist output by the first lens at a distance between the shortest optical path length and the longest optical path length from the first lens to the second lens. Is placed,
The input wavelength selection filter divides the convergent light reflected by the prism mirror into the transmitted light and the reflected light, and the transmitted light is reflected by the mirror and input to the first optical demultiplexer. The reflected light is reflected again by the prism mirror and input to the second optical demultiplexer.
The optical path length from the first lens to the light incident end of the first optical demultiplexer is equal to the optical path length from the first lens to the light incident end of the second optical demultiplexer.
The optical axis of the input light of the first optical demultiplexer and the optical axis of the input light of the second optical demultiplexer are parallel to each other, and the first optical demultiplexer and the second optical demultiplexer are parallel to each other. An optical receiving module in which the optical axes of the signal lights separated by each are all parallel . The optical receiving module according to claim 1, wherein the first optical demultiplexer and the second optical demultiplexer are arranged in a V shape. The optical receiving module according to claim 1, wherein the first optical demultiplexer and the second optical demultiplexer are arranged in parallel. The optical reception according to any one of claims 1 to 3, further comprising a mirror that changes the optical axis of the signal light separated by the first optical demultiplexer and the second optical demultiplexer by 90 °. module. The wavelength multiplex signal light includes 8 channels of signal light, and the first optical demultiplexer includes a wavelength selection filter that separates 4 channels on the long wavelength side or the short wavelength side of the signal light of the 8 channels. The optical receiving module according to any one of claims 1 to 4, wherein the optical demultiplexer 2 includes a wavelength selection filter that separates the remaining 4 channels. The light receiving module according to any one of claims 1 to 5, further comprising a plurality of light receiving elements for receiving signal light collected by the second lens on the downstream side of the second lens. The optical receiving module according to claim 6, wherein the second lens and the light receiving element are integrated for each of the first optical demultiplexer and the second optical demultiplexer.

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