JP2018124429A - Optical module and light output method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical module which can stably output an optical signal by accurately measuring the strength of an optical signal to be output.SOLUTION: The optical module comprises a branch unit 1, a transmission unit 2, a light shielding unit 3, and a light receiving unit 4. The branch unit 1 branches incident signal light into first signal light in a first direction and second signal light in a second direction. The transmission unit 2 is formed on the optical path of the second signal light on the surface of the branch unit 1 in the second direction, and transmits the second signal light. The light shielding unit 3 is formed on the surface of the branch unit 1 in the second direction, and shields light in a direction different from the second direction. The light receiving unit 4 measures the strength of the second signal light. A light shielding layer which does not transmit light by scattering the light is formed on at least one surface out of the surfaces of the branch unit 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for measuring the intensity of an optical signal, and particularly to a technique for improving the accuracy of measuring the intensity of an optical signal.

  An optical module used as a signal light transmitter in an optical communication system is becoming more multifunctional and the number of optical components in the optical module is increasing. On the other hand, when a signal light is wavelength-multiplexed and transmitted, a plurality of optical modules are used in the transmission device. Therefore, each optical module is desirably as small as possible. In addition, an optical module that outputs signal light is required to have a stable intensity of signal light to be output.

  When stabilizing the intensity of the output signal light, a method of branching and measuring the output signal light and controlling the intensity of the output signal light based on the measurement result may be used. The signal light is branched using a prism or the like. However, the signal light can be branched only in a necessary direction, and a part of the light is dispersed as unnecessary light. Such unnecessary light turns into stray light and wraps around the light receiving surface of the light receiving element that measures the intensity of the signal light, thereby degrading the S / N (Signal / Noise) ratio of the measurement result.

  In order to suppress the degradation of the S / N ratio of the measurement result, an optical module additionally mounted with a light shielding plate or a light shielding film that blocks stray light is used so that stray light does not enter the light receiving surface of the light receiving element. There is. However, due to the increase in the number of parts and the miniaturization of the optical module, it is often difficult to secure a sufficient space for arranging the light shielding plate or the like, and it is desirable to be able to suppress the influence of stray light without using the light shielding plate or the like. . For this reason, development of a technique for suppressing the influence of stray light without using a light shielding plate or the like has been performed. As such a technique for suppressing the influence of stray light without using a light shielding plate or the like, for example, a technique as disclosed in Patent Document 1 is disclosed.

  Patent Document 1 relates to an optical device that splits incident light in two directions with a mirror and converts the direction of light in one direction with a prism. In the prism of Patent Document 1, a light-shielding paint is applied to portions other than the incident portion of the light incident surface and the light emitting portion of the light emitting surface in order to prevent stray light.

JP 2005-99293 A

  However, the technique of Patent Document 1 is not sufficient in the following points. In Patent Document 1, a light-absorbing paint having a light shielding property is applied to all surfaces of a prism that changes the direction of light. Therefore, when used for an application in which an optical signal is continuously incident, the optical characteristics of the prism may fluctuate due to an increase in the temperature of the light-absorbing paint portion. For this reason, the technique disclosed in Patent Document 1 may not be able to stably output an optical signal from the optical module.

  In order to solve the above problems, an object of the present invention is to obtain an optical module capable of accurately measuring the intensity of an optical signal to be output and performing stable output.

  In order to solve the above problems, the optical module of the present invention includes a branching section, a transmitting section, a light shielding section, and a light receiving section. The branching unit splits the incident signal light into a first signal light in a first direction and a second signal light in a second direction. The transmission part is formed on the optical path of the second signal light on the surface of the branching part in the second direction, and transmits the second signal light. The light shielding portion is formed on the surface of the branching portion in the second direction, and shields light in a direction different from the second direction. The light receiving unit measures the intensity of the second signal light. Moreover, the light shielding layer which does not permeate | transmit light by scattering light is formed in at least 1 surface among the surfaces of a branch part.

  In the light output method of the present invention, the incident signal light is branched into the first signal light in the first direction and the second signal light in the second direction at the branching unit. According to the light output method of the present invention, the second signal light is transmitted through the transmission portion formed on the optical path of the second signal light on the surface in the second direction of the branching portion. In the light output method of the present invention, light in a direction different from the second direction is shielded by the light shielding portion formed on the surface of the branching portion in the second direction. In the light output method of the present invention, light is blocked by scattering light in a light blocking layer formed on at least one surface among the surfaces of the branch portions. The light output method of the present invention measures the intensity of the second signal light.

  According to the present invention, an optical module capable of accurately measuring the intensity of an optical signal to be output and performing stable output can be obtained.

It is a figure which shows the outline | summary of a structure of the 1st Embodiment of this invention. It is a figure which shows the outline | summary of a structure of the 2nd Embodiment of this invention. It is the figure which showed typically the path | route of the signal light of the 2nd Embodiment of this invention. It is a figure which shows the example of the structure contrasted with the 2nd Embodiment of this invention. It is a figure which shows the example of the structure contrasted with the 2nd Embodiment of this invention. It is a figure which shows the example of the other structure of the 2nd Embodiment of this invention. It is a figure which shows the outline | summary of a structure of the 3rd Embodiment of this invention.

(First embodiment)
A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an outline of the configuration of the optical module of the present embodiment. The optical module of the present embodiment includes a branching unit 1, a transmission unit 2, a light shielding unit 3, and a light receiving unit 4. The branching unit 1 branches the incident signal light into a first signal light in a first direction and a second signal light in a second direction. The transmission unit 2 is formed on the optical path of the second signal light on the surface of the branching unit 1 in the second direction, and transmits the second signal light. The light shielding unit 3 is formed on the surface of the branching unit 1 in the second direction, and shields light in a direction different from the second direction. The light receiving unit 4 measures the intensity of the second signal light. Moreover, the light shielding layer which does not permeate | transmit light is formed in the at least 1 surface among the surfaces of the branch part 1 by scattering light.

  The optical module of the present embodiment includes a light shielding portion 3 on the surface of the branching portion 1 on the path side of the branched second signal light. Therefore, the influence of stray light when measuring the intensity of the second signal light in the light receiving unit 4 can be suppressed. Therefore, the optical module of this embodiment can accurately measure the intensity of the second signal light. Moreover, the branch part 1 of the optical module of the present embodiment includes a light shielding layer that does not transmit light by scattering light on any surface. Since the light shielding layer of the present embodiment does not absorb light, it is possible to suppress the characteristic variation of the branching portion 1. As described above, the optical module according to the present embodiment can accurately measure the intensity of the optical signal to be output and perform stable output.

(Second Embodiment)
A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows the configuration of the optical module of the present embodiment.

  The optical module of the present embodiment includes an optical circuit 11, a prism 12, and a monitor light receiving unit 13. The prism 12 further includes a light shielding layer 14.

  The optical circuit 11 is a signal light output circuit that outputs signal light. The optical circuit 11 includes a semiconductor laser or the like, and generates and outputs signal light. The optical circuit 11 is formed as an optical signal output circuit in a transmitter of an optical communication system, for example. The optical circuit 11 may be a circuit that outputs light other than communication use such as output of light as a light source for measurement. The optical circuit 11 according to the present embodiment controls the output intensity of the signal light to be a set value based on the measurement result of the intensity of the signal light transmitted from the monitor light receiving unit 13. The set value of the output intensity is set based on the design of the system in which the optical module is used.

  The prism 12 branches the signal light incident from the optical circuit 11 into two paths on the output side from the optical module and on the monitor light receiving unit 13 side. The prism 12 is formed as a beam splitter in which two right-angle prisms are bonded together. The prism 12 receives the signal light incident from the optical circuit 11 on the reflection surface in the first direction output from the optical module in the first direction and in the second direction incident on the monitor light receiving unit 13. Branches to the second signal light.

  The signal light on the output side branched in the prism 12, that is, the first signal light is output from the optical module. The signal light on the output side branched in the prism 12 may be output via another unit in the optical module.

  The prism 12 includes a light shielding layer 14 around it. Further, the light shielding layer 14 is not formed on the optical path of the signal light from which the signal light generated by the optical circuit 11 enters the prism 12. In the present embodiment, a region on the optical path for outputting the second signal light to the monitor light receiving unit 13 side on the surface of the prism 12 is referred to as a monitor side transmitting unit 15. The light-shielding layer 14 is not formed in the monitor side transmission part 15. Further, the monitor-side transmission unit 15 of the present embodiment corresponds to the transmission unit 2 of the first embodiment.

  Of the surface of the prism 12, an area on the optical path for outputting the first signal light to the output side is referred to as an output-side transmission unit 16. The light shielding layer 14 is not formed in the output side transmission part 16. That is, each signal light branched by the prism 12 is output without being affected by the light shielding layer 14.

  In addition, a region on the optical path in which signal light is incident on the prism 12 from the optical circuit 11 on the surface of the prism 12 is referred to as an incident-side transmission unit 17. The light-shielding layer 14 is not formed in the incident side transmission part 17. That is, the signal light incident on the prism 12 is not affected by the light shielding layer 14. Further, the prism 12 of the present embodiment corresponds to the branching unit 1 of the first embodiment.

  The light shielding layer 14 is formed on the surface of the prism 12 and scatters stray light, that is, light other than the first signal light and the second signal light. Therefore, the light shielding layer 14 suppresses the emission of stray light from the prism 12 to the outside. The light shielding layer 14 of this embodiment is formed on the monitor light receiving unit 13 side of the prism 12. The light shielding layer 14 can reduce the influence of the stray light on the measurement result of the monitor light receiving unit 13 by suppressing the stray light generated from the prism 12.

  The light shielding layer 14 is formed, for example, as a large number of minute slits on the surface of the prism 12. The minute slits formed in the light shielding layer 14 are formed in all regions other than the respective transmitting portions on the respective surfaces of the prism 12. The minute slits are formed so that the average direction of the slits is not aligned when viewed on one entire surface of the prism 12. By forming a large number of minute slits in the light shielding layer forming region so that their directions are not aligned, stray light is scattered in a random direction on the surface of the light shielding layer 14 and cancels each other. Therefore, stray light emitted from the surface of the prism 12 to the outside can be suppressed. The minute slit is formed, for example, by etching the surface of the prism 12 using a metal mask. When forming minute slits by etching, each transmission part is protected by a metal mask. The minute slits may be patterned using a photoresist.

  The light shielding layer 14 may be formed as a light scattering layer by increasing the surface roughness of the portion of the prism 12 where the light shielding layer 14 is formed. For example, it is possible to form minute irregularities on the surface of the prism 12 by protecting each transmission portion with a metal mask and irradiating the surface of the prism 12 with plasma. The minute irregularities on the surface of the prism 12 function as the light shielding layer 14 because stray light is randomly scattered on the surface. In the case of such a configuration, the surface roughness of the light shielding layer 14 is higher than that of each transmission part. Moreover, after forming the light shielding layer 14, each transmissive part may be subjected to polishing or cleaning in order to improve the transmittance.

  Of the light shielding layer 14 of the present embodiment, the light shielding layer 14 formed on the surface of the prism 12 on the monitor light receiving portion 13 side corresponds to the light shielding portion 3 of the first embodiment.

  The monitor light receiving unit 13 is configured using a photodiode. The monitor light receiving unit 13 converts the signal light branched by the prism 12 into an electrical signal and measures the intensity. The monitor light receiving unit 13 sends the measurement result of the intensity of the signal light branched by the prism 12 to the optical circuit 11. The measurement result of the intensity of the signal light may be output to another circuit using the measurement result other than the optical circuit 11. Further, the monitor light receiving unit 13 of the present embodiment corresponds to the light receiving unit 4 of the first embodiment.

  The operation of the optical module of this embodiment will be described. When the optical module starts operation, first, signal light is output from the optical circuit 11 of the optical module to the prism 12. The signal light is incident on the prism 12 from the incident side transmitting portion 17. When the signal light is incident, the prism 12 branches the signal light into the two paths on the output side and the monitor light receiving unit 13 side as the first signal light and the second signal light. The branched first signal light and second signal light are respectively output to the output side of the optical module and the monitor light receiving unit 13 via the output side transmission unit 16 and the monitor side transmission unit 15.

  The signal light input to the prism 12 is branched into two, and stray light is generated in the prism 12 at that time. The stray light generated by the prism 12 travels to the periphery of the prism 12. Since the light shielding layer 14 is formed on the surface portion of the prism 12, the stray light is scattered in a random direction by the light shielding layer 14 on the surface of the prism 12. Therefore, strong stray light is not emitted from the prism 12. That is, stray light is shielded by the light shielding layer 14 and does not go out of the prism 12. Therefore, the monitor light receiving unit 13 is not easily affected by stray light caused by the prism 12 in measuring the intensity of the signal light.

  The first signal light branched by the prism 12 and sent to the output side of the optical module is output from the optical module. Further, the second signal light branched by the prism 12 and sent to the monitor light receiving unit 13 is received by the photodiode of the monitor light receiving unit 13.

  When the monitor light receiving unit 13 receives the second signal light branched by the prism 12, the monitor light receiving unit 13 measures the intensity of the second signal light. When the intensity of the second signal light is measured, the monitor light receiving unit 13 sends the measurement result to the optical circuit 11. When receiving the measurement result of the intensity of the second signal light, the optical circuit 11 controls the intensity of the output signal light to be a set value and outputs the signal light to the prism 12. The optical module can output signal light with stable intensity by repeating the above operation.

  FIG. 4 shows an example of the configuration of an optical module in which the light shielding layer is not formed on the prism as an example of the configuration compared with the configuration of the optical module of the present embodiment. In the optical module of FIG. 4, since the intensity of stray light is not weakened on the surface of the prism, the stray light radiated to the outside from the prism is reflected by the side wall or the like inside the optical module and enters the monitor light receiving unit. Therefore, in the optical module of FIG. 4, since the stray light is detected as noise by the monitor light receiving unit, the intensity of the signal light branched from the output light from the optical circuit cannot be measured accurately. Therefore, the optical circuit of the optical module in FIG. 4 cannot output signal light having a stable intensity.

  FIG. 5 shows an example of the configuration of an optical module provided with a light shielding plate for removing stray light incident on the monitoring diode as an example of another configuration compared with the configuration of the optical module of the present embodiment. It is. Although the influence of the stray light on the monitor light receiving unit can be reduced by providing the light shielding plate as shown in FIG. 5, the size of the optical module increases due to the arrangement of the light shielding plate. In addition, the degree of freedom in designing the optical module is reduced because an appropriate light shielding plate is disposed.

  In contrast to the optical module configured as shown in FIGS. 4 and 5, the optical module of the present embodiment includes the light shielding layer 14 on the surface of the prism 12, so that stray light generated from the prism 12 is emitted to the monitor light receiving unit 13 side. Is suppressed. Therefore, when measuring the intensity of the signal light in the monitor light receiving unit 13, it is difficult to be affected by stray light, so that the intensity of the signal light can be accurately measured. As a result, the optical module of this embodiment can keep the intensity of the output signal light stable.

  Further, the prism 12 of the optical module of this embodiment has the light shielding layer 14 formed on all surfaces, but the light shielding layer 14 may be formed only on the surface on the monitor light receiving unit 13 side as shown in FIG. . FIG. 6 shows an example of the configuration of an optical module including the prism 12 in which the light shielding layer 14 is formed only on the surface on the monitor light receiving unit 13 side. When the light shielding layer 14 is formed only on the surface on the monitor light receiving unit 13 side, a light shielding structure that suppresses the influence of stray light from the other surface of the prism 12 may be provided. Further, the light shielding layer 14 may be formed only on the surface of the prism 12 on the monitor light receiving unit 13 side and the surface adjacent to the surface. By adopting such a configuration, stray light can escape from the prism 12 from the surface having the least influence on the monitor light receiving unit 13.

  In the optical module of this embodiment, in the light shielding layer 14 formed on the surface of the prism 12, the direction of stray light other than signal light is changed by scattering to suppress the influence of stray light emitted from the prism 12. Therefore, when the intensity of the signal light branched by the prism 12 is measured by the monitor light receiving unit 13, noise caused by stray light can be suppressed, so that the intensity of the signal light can be accurately measured. Therefore, it is possible to stably control the output signal light based on the accurate measurement result of the intensity of the signal light in the optical circuit 11. As a result, the optical module of the present embodiment can accurately measure the intensity of the output optical signal and perform stable output.

(Third embodiment)
A third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 7 shows an outline of the configuration of the optical module of the present embodiment. In the second embodiment, the light shielding layer 14 using light scattering is formed on the surface of the prism 12 on the monitor light receiving unit 13 side. However, the prism 12 of the optical module of the present embodiment is a light absorbing layer, that is, It is characterized by comprising a light shielding layer made of a light absorbing film.

  The optical module of the present embodiment includes an optical circuit 11, a prism 12, and a monitor light receiving unit 13. The prism 12 further includes a light shielding layer 14 and a light absorbing layer 21. The configurations and functions of the optical circuit 11 and the monitor light receiving unit 13 of the present embodiment are the same as the parts having the same names in the second embodiment.

  The configuration and function of the prism 12 main body are the same as those of the prism 12 of the second embodiment. Further, a light absorbing layer 21 is formed on the surface of the prism 12 of the present embodiment on the monitor light receiving unit 13 side. Moreover, the light shielding layer 14 is formed on the surface other than the surface on which the light absorption layer 21 is formed.

  Similarly to the second embodiment, on the incident side of the signal light from the optical circuit 11 and the optical path for outputting the branched signal light, the incident-side transmission unit 17, the monitor-side transmission unit 15, and the output-side transmission are provided. Each part 16 is formed.

  The light absorbing layer 21 is formed by depositing a light absorbing material, that is, a material that absorbs light. The light absorption layer 21 is formed by depositing a light absorption material by coating or printing.

  The operation of the optical module of this embodiment will be described. In the present embodiment, the signal light incident on the prism 12 from the optical circuit 11 is branched into the first signal light and the second signal light, and the optical circuit 11 is based on the measurement result of the intensity of the second signal light. The operation when controlling the intensity of the signal light output from is the same as in the second embodiment. Therefore, hereinafter, only the behavior of stray light generated in the prism 12 when the signal light is incident and branched will be described.

  The signal light incident on the prism 12 is branched into two. At this time, stray light is generated in the prism 12 as in the second embodiment. The stray light generated by the prism 12 travels to the periphery of the prism 12. A light shielding layer 14 and a light absorbing layer 21 are formed on the surface portion of the prism 12. The stray light that has traveled to the surface on which the light shielding layer 14 is formed is scattered by the light shielding layer 14 on the surface of the prism 12, so that light with high intensity is not emitted from the prism 12. Therefore, the stray light is shielded by the light shielding layer 14 and does not go out of the prism 12. The stray light that has traveled to the surface on which the light absorption layer 21 is formed is absorbed by the light absorption layer 21 formed on the surface of the prism 12. Therefore, the stray light that has traveled to the surface on which the light absorption layer 21 is formed is not emitted from the light absorption layer 21. That is, the stray light generated in the prism 12 is not radiated from any surface of the prism 12. Therefore, the stray light generated from the prism 12 does not affect the measurement of the intensity of the second signal light in the monitor light receiving unit 13. As a result, the optical circuit 11 can stably control the signal light output based on the measurement result of the intensity of the second signal light.

  The optical module of this embodiment has the same effect as the optical module of the second embodiment. Further, the optical module of the present embodiment includes a light absorbing layer 21 on the surface of the prism 12 on the monitor light receiving unit 13 side. Therefore, since the stray light can be completely blocked by light absorption in the light absorption layer 21, the stray light emitted to the monitor light receiving unit 13 side can be greatly reduced. Therefore, in this embodiment, the intensity of the signal light branched by the prism 12 in the monitor light receiving unit 13 can be measured more accurately. Further, in the optical module of this embodiment, the surface other than the monitor light receiving unit 13 side is shielded by the light shielding layer 14, and stray light emitted from the prism 12 is reduced by scattering. Therefore, since the stray light is not absorbed on the surface other than the monitor light receiving unit 13 side, the characteristic variation of the prism 12 due to the temperature rise or the like hardly occurs. Therefore, the prism 12 of the present embodiment can more stably branch and output the signal light. As a result, the optical module of this embodiment can measure the intensity of the optical signal to be output more accurately and perform stable output.

DESCRIPTION OF SYMBOLS 1 Branch part 2 Transmission part 3 Light-shielding part 4 Light-receiving part 11 Optical circuit 12 Prism 13 Monitor light-receiving part 14 Light-shielding layer 15 Monitor side transmission part 16 Output side transmission part 17 Incident side transmission part 21 Light absorption layer

Claims (10)

A branching unit that branches the incident signal light into a first signal light in a first direction and a second signal light in a second direction;
A transmission part that is formed on the optical path of the second signal light on the surface of the branch part in the second direction, and transmits the second signal light;
A light shielding portion that is formed on a surface of the branch portion in the second direction and shields light in a direction different from the second direction;
A light receiving unit for measuring the intensity of the second signal light,
An optical module, wherein a light shielding layer that does not transmit light by scattering light is formed on at least one of the surfaces of the branch portion.   The optical module according to claim 1, wherein the light shielding layer is formed as the light shielding portion on the surface in the second direction.   The said light shielding part of the surface of the said 2nd direction is formed of the light absorption film | membrane, and the said light shielding layer is formed in the said surfaces other than the said 2 direction, The said light shielding part is characterized by the above-mentioned. Optical module.   The optical module according to claim 1, wherein the light shielding layer scatters the light by a slit pattern.   5. The optical module according to claim 1, wherein the light shielding layer is formed to have a surface roughness higher than that of the transmissive portion. A signal light generation unit that generates and outputs the signal light incident on the branch unit;
The said signal light production | generation part controls the intensity | strength of the said signal light to output based on the intensity | strength of the said 2nd signal light which the said light-receiving part measures, The Claim 1 to 5 characterized by the above-mentioned. Optical module. The incident signal light is branched at a branching portion that branches the first signal light in the first direction and the second signal light in the second direction,
In the transmission part formed on the optical path of the second signal light on the surface of the branch part in the second direction, the second signal light is transmitted,
In the light shielding portion formed on the surface of the branch portion in the second direction, light in a direction different from the second direction is shielded,
The light is blocked by scattering light in a light blocking layer formed on at least one of the surfaces of the branch part,
An optical output method comprising measuring the intensity of the second signal light.   The light output method according to claim 1, wherein the light shielding layer is formed as the light shielding portion.   The light shielding portion on the surface in the second direction is formed of a light-absorbing film, and the light shielding layer is formed on the surface in a direction other than the second direction. Light output method. Generating the signal light incident on the branching section and outputting it to the branching section;
10. The light output method according to claim 7, wherein the intensity of the signal light output to the branching unit is controlled based on the measured intensity of the second signal light.

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