Optical module and optical transceiver

Abstract

To provide an optical module and the like capable of contributing to a reduction in size of a module main body while ensuring a stable mode filter function.SOLUTION: An optical module includes an optical transmitter that outputs transmission light to a transmission path port using an optical signal, and an optical receiver that receives reception light from the transmission path port using the optical signal. An optical module includes an optical fiber that is an SMF (Single Mode Fiber), which connects the optical transmitter and the optical receiver to the transmission path port, and through which the optical signal propagates. A wavelength of the optical signal is equal to or less than a cutoff wavelength of the optical fiber. The optical module includes a holding mechanism that holds a bending shape of the optical fiber having a predetermined radius of curvature and through which only a basic mode in the optical signal propagates.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical module and an optical transceiver. [Background technology]

[0002] For example, with the development of the Internet, the amount of traffic at large-scale data centers continues to increase dramatically. In the future, the introduction of 5G mobile communication systems is expected to progress, and a data-driven society utilizing advances in AI (Artificial Intelligence) and machine learning, IoT (Internet of Things) that connects a huge number of sensors and devices, and autonomous driving technology, etc., is expected to be realized. Therefore, as the introduction of 5G progresses, the amount of traffic is increasing at an accelerating rate.

[0003] In 5G, for example, approximately 100 5G antenna base stations exist within a cell with a radius of 2 km. Furthermore, in 6G, it is expected that radio frequencies will be further increased and cell radii will be smaller. Therefore, for example, if the cell radius of a 6G antenna base station is 20 m, approximately 10,000 6G antenna base stations will be required within a 2 km cell. Furthermore, 6G is expected to achieve high-speed communications of, for example, 1 terabit per second (TBP), which is even faster than 100 Gbps.

[0004] Conventional 3G and 4G base stations are installed in or near telecommunications carrier buildings and are connected to the network, but 5G and 6G base stations are increasingly using optical fronthaul, which extends optical fiber from 3G and 4G base stations or telecommunications carrier buildings where base stations are installed.

[0005] Therefore, there is a demand for the development of optical modules such as optical transceivers that incorporate 100 Gbps class single-core bidirectional optical devices using single-mode fiber over distances of less than 10 km by 2030.

[0006] In optical modules, for example, when an optical signal with a wavelength in the 1 μm band is transmitted through a 1.3 μm band SMF (Single Mode Fiber) optical fiber, higher-order modes are generated due to the effects of reflections on the transmission path along which the optical signal propagates. As a result, higher-order modes affect the fundamental mode, causing transmission degradation. Therefore, in long-distance transmission and high-bit-rate transmission, mode filters are required to remove higher-order modes. Note that 1.3 μm band SMF is an optical fiber capable of transmitting 1.3 μm band optical signals in the fundamental mode.

[0007] An example of a mode filter is a higher-order mode filter that uses a bent optical fiber. A higher-order mode filter requires a structure that precisely maintains the radius of curvature so that the fundamental mode is not radiated while radiating the higher-order mode propagating through the waveguide by bending the optical fiber.

[0008] In high-order mode filters that use a bending method for optical fibers, the possibility of the optical fiber breaking generally increases when the optical fiber is bent at a small curvature, so there is also a need to improve the bending strength of the optical fiber.

[0009] Fig. 17 is an explanatory diagram showing an example of a conventional optical module 100. The optical module 100 shown in Fig. 17 has a substrate 101, a housing 102, an optical fiber 103, a transmission line port 105, and a mandrel 104. An optical transmitter 106 and an optical receiver 107 are mounted on the substrate 101. The housing 102 is a housing for the optical module 100 for mounting the substrate 101. The transmission line port 105 is an input / output port that connects the optical fiber 103 to an external transmission line (not shown).

[0010] One end of the optical fiber 103 is connected to an optical transmitter 106 and an optical receiver 107 in the substrate 101, and the other end is connected to a transmission line port 105. The mandrel 104 forms and maintains a bent shape by winding the optical fiber 103 around the mandrel 104. As a result, the bent shape of the optical fiber 103 wound around the mandrel 104 functions as a mode filter that removes higher-order modes of the optical signal propagating through the optical fiber 103.

[0011] The optical module 100 can suppress transmission degradation of the optical signal by radiating higher-order modes from the optical signal propagating through the bent optical fiber 103 and propagating only the fundamental mode. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] US Patent Application Publication No. 2019 / 0115722 [Patent Document 2] Patent Publication No. 2021-189252 [Patent Document 3] U.S. Patent No. 10,191,221 Summary of the Invention [Problem to be solved by the invention]

[0013] However, in the conventional optical module 100, the stress of the optical fiber 103 itself wound around the mandrel 104 causes the radius of curvature of the optical fiber 103 to be unstable, making it difficult for the optical fiber 103 to function stably as a mode filter.

[0014] Furthermore, in the optical module 100, it is conceivable that the optical axis may be misaligned at the optical coupling point where the optical fiber 103 is connected due to stress on the optical fiber 103 itself when it is wound around the mandrel 104. Examples of optical coupling points include the optical coupling point between the transmission line port 105 that connects to the other end of the optical fiber 103, and the optical coupling points between the optical transmitter 106 and the optical receiver 107 that connect to one end of the optical fiber 103.

[0015] Furthermore, it is expected that future optical modules will have multiple optical fibers 103 arranged in an array (parallel), and since the influence of stress on the optical fibers 103 tends to increase further, it is conceivable that the misalignment of the optical axes at the optical coupling points will increase further.

[0016] Furthermore, in future optical modules, the component packaging density will increase, but since it will be necessary to ensure an installation area for the mandrel 104, the module body will become larger.

[0017] Therefore, in the future, there will be a demand for optical modules that can contribute to miniaturization of the module body while ensuring stable mode filter function.

[0018] In one aspect, an object of the present invention is to provide an optical module or the like that can contribute to miniaturization of the module body while ensuring a stable mode filter function. [Means for solving the problem]

[0019] An optical module of one embodiment includes an optical transmitter that outputs transmitted light to a transmission line port using an optical signal, and an optical receiver that receives received light from the transmission line port using the optical signal. The optical module connects the optical transmitter and the optical receiver to the transmission line port and includes an SMF (Single Mode Fiber) optical fiber through which the optical signal propagates. The wavelength of the optical signal is equal to or shorter than the cutoff wavelength of the optical fiber. The optical module includes a holding mechanism that holds the bent shape of the optical fiber with a predetermined radius of curvature, through which only the fundamental mode of the optical signal propagates. [Effects of the Invention]

[0020] According to one aspect, it is possible to contribute to miniaturization of the module body while ensuring a stable mode filter function. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of an optical module according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram illustrating an example of an optical module according to a second embodiment. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of a holding mechanism of an optical module according to a third embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a holding mechanism of an optical module according to a fourth embodiment. [Figure 5] FIG. 5 is an explanatory diagram showing an example of a holding mechanism of an optical module according to a fifth embodiment. [Figure 6] FIG. 6 is an explanatory diagram showing an example of a holding mechanism of an optical module according to a sixth embodiment. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of an optical module according to a seventh embodiment. [Figure 8] FIG. 8 is an explanatory diagram illustrating an example of an optical module according to an eighth embodiment. [Figure 9] FIG. 9 is an explanatory diagram illustrating an example of an optical module according to a ninth embodiment. [Figure 10] FIG. 10 is an explanatory diagram showing an example of an optical module according to a tenth embodiment. [Figure 11] FIG. 11 is an explanatory diagram illustrating an example of an optical module according to an eleventh embodiment. [Figure 12] FIG. 12 is an explanatory diagram showing an example of a cross section taken along line AA shown in FIG. [Figure 13] FIG. 13 is an explanatory diagram illustrating an example of an optical module according to a twelfth embodiment. [Figure 14] FIG. 14 is an explanatory diagram showing an example of a cross section taken along line BB shown in FIG. [Figure 15] FIG. 15 is an explanatory diagram showing an example of an optical module according to a thirteenth embodiment. [Figure 16] FIG. 16 is an explanatory diagram showing an example of an optical transceiver according to this embodiment. [Figure 17] FIG. 17 is an explanatory diagram showing an example of a conventional optical module. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, examples of the optical module and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to these examples. Furthermore, the examples shown below may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0023] FIG. 1 is an explanatory diagram illustrating an example of an optical module 1 according to a first embodiment. The optical module 1 illustrated in FIG. 1 is, for example, a single-fiber bidirectional optical device. The optical module 1 includes a substrate 2, a housing 3, an optical fiber 4, a holding mechanism 5, and a transmission line port 11. An optical transmitter 12 and an optical receiver 13 are mounted on the substrate 2. The optical transmitter 12 is an optical component such as an optical modulator or a light-emitting element, which modulates an optical signal from a light-emitting element into transmission light based on an electrical signal corresponding to transmission data, and outputs the modulated transmission light to the transmission line port 11 via the optical fiber 4. The optical transmitter 12 is, for example, a VCSEL (Vertical Cavity Surface Emitting Laser) transmitter. The optical transmitter 12 typically uses signal light in the 857-nanometer band, but can also use transmission light in the 1-micrometer band.

[0024] The optical receiver 13 is an optical component such as an optical hybrid circuit or a light receiving element that receives the incoming light from the transmission line port 11 using an optical signal and obtains an electrical signal corresponding to the received data from the received light. The housing 3 is a housing for the optical module 1 on which the substrate 2 is mounted. The transmission line port 11 is an input / output port that connects the optical fiber 4 to an external transmission line (not shown).

[0025] One end of the optical fiber 4 is connected to the optical transmitter 12 and optical receiver 13 in the substrate 2, and the other end is connected to the transmission line port 11. The optical fiber 4 connects the optical transmitter 12 and optical receiver 13 to the transmission line port 11, and is an optical fiber, for example, SMF (Single Mode Fiber), through which an optical signal propagates. The optical signal uses a wavelength band of, for example, 1.26 μm or less, which is the cutoff wavelength of SMF optical fiber compatible with the 1.3 μm band.

[0026] The optical fiber 4 is a mode filtering fiber having a curved shape with a predetermined radius of curvature that removes higher-order modes of the propagating optical signal by emitting the higher-order modes, and also exhibits a mode filter function that allows only the fundamental mode other than the higher-order modes to propagate.

[0027] Furthermore, the holding mechanism 5 is a mechanism that is mounted on the substrate 2 and that holds the bent shape of the optical fiber 4 having a predetermined radius of curvature. Since the optical fiber 4 is held in a bent shape having a predetermined radius of curvature by the holding mechanism 5, only the fundamental mode of the optical signal propagating between the optical transmitter 12 and the transmission line port 11 and between the optical receiver 13 and the transmission line port 11 is propagated.

[0028] The holding mechanism 5 holds the bent shape of the optical fiber 4 with a predetermined radius of curvature, thereby suppressing misalignment of the optical axis at the optical coupling point between the optical transmitter 12 and the optical receiver 13 connected to one end of the optical fiber 4, and at the optical coupling point between the transmission line port 11 connected to the other end of the optical fiber 4.

[0029] In the optical module 1 of the first embodiment, the substrate 2 is provided with a holding mechanism 5 that holds the bent shape of the optical fiber 4 with a predetermined radius of curvature that allows it to function as a mode filter. As a result, the holding mechanism 5 holds the bent shape with the predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing the module body to be made more compact. Moreover, because the optical fiber 4 is held by the holding mechanism 5, the probability of breakage and optical axis misalignment of the optical fiber 4 can be reduced while suppressing stress on the optical fiber 4 itself.

[0030] In the optical module 1 of Example 1, the holding mechanism 5 is mounted on the substrate 2, but this is not limited to this, and the holding mechanism 5 may also be mounted on the housing 3, and this embodiment will be described below as Example 2. [Example]

[0031] 2 is an explanatory diagram showing an example of an optical module 1A of Example 2. Note that the same components as those in the optical module 1 of Example 1 are given the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical module 1 of Example 1 differs from the optical module 1A of Example 2 in that a holding mechanism 5A for holding the bent shape of an optical fiber 4A having a predetermined radius of curvature is mounted on the housing 3.

[0032] The holding mechanism 5A is mounted on the housing 3 and holds the bent shape of the optical fiber 4A with a predetermined radius of curvature that enables the optical fiber 4A to exhibit a mode filter function. Since the bent shape with the predetermined radius of curvature of the optical fiber 4A is held by the holding mechanism 5A, only the fundamental mode of the optical signal propagating between the optical transmitter 12 and the transmission line port 11 and between the optical receiver 13 and the transmission line port 11 is propagated.

[0033] The holding mechanism 5A holds the bent shape of the optical fiber 4A with a predetermined radius of curvature, thereby suppressing misalignment of the optical axis at the optical coupling points between the optical transmitter 12 and the optical receiver 13, which are connected to one end of the optical fiber 4A, and at the optical coupling points between the transmission line port 11, which is connected to the other end of the optical fiber 4A.

[0034] In the optical module 1A of the second embodiment, a holding mechanism 5A is provided in the housing 3 to hold the bent shape of the optical fiber 4A with a predetermined radius of curvature that enables the optical fiber 4A to function as a mode filter. As a result, the holding mechanism 5A holds the bent shape with the predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing for a more compact module body. Moreover, because the optical fiber 4A is held by the holding mechanism 5A, the probability of breakage and optical axis misalignment of the optical fiber 4A can be reduced while suppressing stress on the optical fiber 4A itself.

[0035] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and one example of this embodiment will be described below as Example 3. [Example]

[0036] 3 is an explanatory diagram showing an example of a holding mechanism 5B of an optical module 1B according to a third embodiment. The same components as those in the optical module 1 of the first embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. FIG. 3 shows the main part of the holding mechanism 5B mounted on the substrate 2, and does not show the optical transmitter 12, the optical receiver 13, the housing 3, etc. The holding mechanism 5B shown in FIG. 3 is mounted on the substrate 2 and has a first holding part 5B1 disposed on one end of the surface of the substrate 2, and a second holding part 5B2 disposed on the other end of the surface of the substrate 2.

[0037] The first holding unit 5B1 has two first struts 5B11 and holds one end of the optical fiber 4. The first holding unit 5B1 holds the outer and inner circumferences of one end of the optical fiber 4 by sandwiching a part of the optical fiber 4 between the two first struts 5B11.

[0038] The second holding part 5B2 has two second struts 5B21 and holds the other end of the optical fiber 4. The second holding part 5B2 holds the outer and inner circumferences of the other end of the optical fiber 4 by sandwiching a part of the optical fiber 4 between the two second struts 5B21.

[0039] The holding mechanism 5B holds one end of the optical fiber 4 between two first struts 5B11 in the first holding section 5B1, and holds the other end of the optical fiber 4 between two second struts 5B21 in the second holding section 5B2. As a result, the holding mechanism 5B forms and holds the bent shape of the optical fiber 4 having a predetermined radius of curvature.

[0040] In other words, the two first pillars 5B11 in the first holding portion 5B1 and the two second pillars 5B21 in the second holding portion 5B2 are positioned at surface positions on the substrate 2 where the optical fiber 4 can be held in a shape with a predetermined radius of curvature.

[0041] The holding mechanism 5B in the optical module 1B of the third embodiment holds one end of the optical fiber 4 from both the inner and outer diameters by sandwiching one end of the optical fiber 4 between two first support columns 5B11 in a first holding unit 5B1 arranged on one end of the substrate 2. The holding mechanism 5B holds the other end of the optical fiber 4 from both the inner and outer diameters by sandwiching the other end of the optical fiber 4 between two second support columns 5B21 in a second holding unit 5B2 arranged on the other end of the substrate 2. The holding mechanism 5B then forms and holds the bent shape of the optical fiber 4 using the first holding unit 5B1 and the second holding unit 5B2. As a result, the holding mechanism 5B maintains a bent shape with a predetermined curvature radius, ensuring stable mode filter function. Since a mandrel, as in the conventional method, is not required, the module body can be made more compact. Moreover, since the optical fiber 4 is held by the holding mechanism 5B, stress on the optical fiber 4 itself can be suppressed, while the probability of breakage and optical axis misalignment of the optical fiber 4 can be reduced.

[0042] In the optical module 1A of the second embodiment, the case where the holding mechanism 5A is mounted on the housing 3 is exemplified, and one example of this embodiment will be described below as a fourth embodiment. [Example]

[0043] FIG. 4 is an explanatory diagram showing an example of a holding mechanism 5C of an optical module 1C according to a fourth embodiment. The same components as those in the optical module 1A of the second embodiment are denoted by the same reference numerals, and redundant descriptions of the components and operations will be omitted. FIG. 4 shows a main part of the holding mechanism 5C mounted on the housing 3, and does not show the board 2 on which the optical transmitter 12 and the optical receiver 13 are mounted. The holding mechanism 5C shown in FIG. 4 is mounted on the housing 3 and has a first holding part 5C1 disposed on one end of the surface of the housing 3, and a second holding part 5C2 disposed on the other end of the surface of the housing 3.

[0044] The first holding unit 5C1 has two first struts 5C11 and holds one end of the optical fiber 4 A. The first holding unit 5C1 holds the outer and inner circumferences of one end of the optical fiber 4 A by sandwiching a part of the optical fiber 4 A between the two first struts 5C11.

[0045] The second holding unit 5C2 has two second struts 5C21 and holds the other end of the optical fiber 4 A. The second holding unit 5C2 holds the outer and inner circumferences of the other end of the optical fiber 4 A by sandwiching a part of the optical fiber 4 A between the two second struts 5C21.

[0046] The holding mechanism 5C holds one end of the optical fiber 4A between two first struts 5C11 in the first holding unit 5C1, and holds the other end of the optical fiber 4A between two second struts 5C21 in the second holding unit 5C2. As a result, the holding mechanism 5C forms and holds the bent shape of the optical fiber 4A having a predetermined radius of curvature.

[0047] In other words, the two first pillars 5C11 in the first holding portion 5C1 and the two second pillars 5C21 in the second holding portion 5C2 are positioned at surface positions on the housing 3 where the optical fiber 4A can be held in a shape with a predetermined radius of curvature.

[0048] The holding mechanism 5C in the optical module 1C of the fourth embodiment holds one end of the optical fiber 4A from both the inner and outer diameters by sandwiching one end of the optical fiber 4A between two first struts 5C11 in a first holding unit 5C1 arranged on one end of the housing 3. The holding mechanism 5C holds the other end of the optical fiber 4A from both the inner and outer diameters by sandwiching the other end of the optical fiber 4A between two second struts 5C21 in a second holding unit 5C2 arranged on the other end of the housing 3. The holding mechanism 5C then forms and holds the bent shape of the optical fiber 4A using the first holding unit 5C1 and the second holding unit 5C2. As a result, the holding mechanism 5C maintains a bent shape with a predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional case, thereby enabling the module body to be made more compact. Moreover, since the optical fiber 4A is held by the holding mechanism 5C, the probability of breakage and optical axis misalignment of the optical fiber 4A can be reduced while suppressing stress on the optical fiber 4A itself.

[0049] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and one example of this embodiment will be described below as Example 5. [Example]

[0050] FIG. 5 is an explanatory diagram showing an example of a holding mechanism 5D of an optical module 1D according to a fifth embodiment. The same components as those in the optical module 1 of the first embodiment are denoted by the same reference numerals, and redundant descriptions of the components and operations will be omitted. FIG. 5 shows a main part of the holding mechanism 5D mounted on a substrate 2, and does not include an optical transmitter 12, an optical receiver 13, a housing 3, etc. The holding mechanism 5D shown in FIG. 5 has a holding groove 5D1 engraved into the surface of the substrate 2 to hold the optical fiber 4. The holding mechanism 5D forms and holds the optical fiber 4 in a bent shape having a predetermined radius of curvature by routing the optical fiber 4 within the holding groove 5D1. The holding groove 5D1 holds the entire optical fiber 4 from the inner and outer diameters.

[0051] That is, the holding groove 5D1 is formed on the surface of the substrate 2 in a size and shape that allows the optical fiber 4 to be held while forming a shape with a predetermined radius of curvature.

[0052] The holding mechanism 5D in the optical module 1D of the fifth embodiment forms and holds the optical fiber 4 in a bent shape having a predetermined radius of curvature that enables the optical fiber 4 to function as a mode filter by routing the optical fiber 4 in a holding groove 5D1 provided on the surface of the substrate 2. As a result, the holding mechanism 5D holds the bent shape having the predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional method, thereby enabling the module body to be made more compact. Moreover, because the optical fiber 4 is held by the holding mechanism 5D, the probability of breakage and optical axis misalignment of the optical fiber 4 can be reduced while suppressing stress on the optical fiber 4 itself.

[0053] In the optical module 1A of the second embodiment, the case where the holding mechanism 5A is mounted on the housing 3 is exemplified, and one example of this embodiment will be described below as a sixth embodiment. [Example]

[0054] FIG. 6 is an explanatory diagram showing an example of a holding mechanism 5E of an optical module 1E according to a sixth embodiment. The same components as those in the optical module 1A according to the second embodiment are designated by the same reference numerals, and redundant descriptions of the components and operations will be omitted. FIG. 6 shows a main part of the holding mechanism 5E provided in the housing 3, and does not show the substrate 2 on which the optical transmitter 12 and the optical receiver 13 are mounted. The holding mechanism 5E shown in FIG. 6 is provided by carving into the surface of the housing 3 and has a holding groove 5E1 for holding the optical fiber 4A. The holding mechanism 5E forms and holds the bent shape of the optical fiber 4A having a predetermined radius of curvature by routing the optical fiber 4A within the holding groove 5E1. The holding groove 5E1 holds the entire optical fiber 4A from the inner and outer diameters.

[0055] That is, the holding groove 5E1 is formed on the surface of the housing 3 in a size and shape that allows the optical fiber 4A to be held while forming a shape with a predetermined radius of curvature.

[0056] The holding mechanism 5E in the optical module 1E of Example 6 forms and holds the optical fiber 4A in a bent shape having a predetermined radius of curvature that enables the optical fiber 4A to function as a mode filter by routing the optical fiber 4A within a holding groove 5E1 provided on the surface of the housing 3. As a result, the holding mechanism 5E maintains a bent shape having a predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional method, thereby enabling the module body to be made more compact. Moreover, because the optical fiber 4A is held by the holding mechanism 5E, the probability of breakage and optical axis misalignment of the optical fiber 4A can be reduced while suppressing stress on the optical fiber 4A itself.

[0057] Although the optical module 1 of Example 1 is illustrated as being provided with the holding mechanism 5 on the substrate 2 for holding the bent shape of the optical fiber 4 having a predetermined radius of curvature, the bent shape of the optical fiber 4 may be a preform, and can be changed as appropriate. Therefore, an embodiment in which the bent shape of the optical fiber 4 is a preform will be described below as Example 7. [Example]

[0058] 7 is an explanatory diagram showing an example of an optical module 1F of Example 7. For ease of explanation, the same components as those in the optical module 1 of Example 1 are given the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical module 1F of Example 7 differs from the optical module 1 of Example 1 in that an optical fiber 4F preformed into a bent shape with a predetermined radius of curvature using thermal stress relaxation is used as a holding mechanism 5F.

[0059] The optical fiber 4F is an optical fiber in a bent shape with a predetermined radius of curvature, with stress in the optical fiber 4F itself being relieved by heat treatment. The holding mechanism 5F is configured from the optical fiber 4F preformed into a bent shape with a predetermined radius of curvature, and fixes the optical fiber 4F to the substrate 2 with an adhesive while maintaining the bent shape of the optical fiber 4F with the predetermined radius of curvature.

[0060] In the optical module 1F of Example 7, the stress in the optical fiber 4F itself is relieved by heat treatment, and the bent shape of the optical fiber 4F is maintained with a predetermined radius of curvature that allows the optical fiber 4F to exhibit mode filter function. As a result, the optical fiber 4F maintains a bent shape with a predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing the module body to be made more compact. Moreover, because the optical fiber 4F whose stress has been relieved by heat treatment is used, the probability of breakage and optical axis misalignment of the optical fiber 4F can be reduced while suppressing the stress in the optical fiber 4F itself.

[0061] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and an embodiment of this example will be described below as Example 8. [Example]

[0062] Fig. 8 is an explanatory diagram showing an example of an optical module 1G according to an eighth embodiment. Note that the same components as those in the optical module 1 of the first embodiment are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The holding mechanism 5G shown in Fig. 8 is mounted on the substrate 2 and has a frame-shaped first holding part 5G1 arranged on one end side of the surface of the substrate 2, and a frame-shaped second holding part 5G2 arranged on the other end side of the surface of the substrate 2.

[0063] The first holding unit 5G1 holds the outer and inner circumferences of one end of the optical fiber 4, which has a predetermined radius of curvature. The second holding unit 5G2 holds the outer and inner circumferences of the other end of the optical fiber 4, which has a predetermined radius of curvature. The holding mechanism 5G uses the first holding unit 5G1 and the second holding unit 5G2 to hold the bent shape of the optical fiber 4, which has a predetermined radius of curvature, on the surface of the substrate 2.

[0064] That is, the first holding portion 5G1 and the second holding portion 5G2 are arranged at surface positions on the substrate 2 that can hold the bent shape of the optical fiber 4 with a predetermined radius of curvature.

[0065] The holding mechanism 5G in the optical module 1G of Example 8 holds one end of the optical fiber 4 from the inner and outer diameters using a first holding unit 5G1 arranged on one end of the substrate 2. The holding mechanism 5G holds the other end of the optical fiber 4 from the inner and outer diameters using a second holding unit 5G2 arranged on the other end of the substrate 2. The holding mechanism 5G then uses the first holding unit 5G1 and the second holding unit 5G2 to maintain the bent shape of the optical fiber 4 with a predetermined radius of curvature that enables the mode filter function to be exhibited. As a result, the holding mechanism 5G maintains the bent shape with a predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional method, thereby enabling the module body to be made more compact. Moreover, because the optical fiber 4 is held by the holding mechanism 5G, the probability of breakage and optical axis misalignment of the optical fiber 4 can be reduced while suppressing stress on the optical fiber 4 itself.

[0066] In the optical module 1A of the second embodiment, the case where the holding mechanism 5H is mounted on the housing 3 is exemplified, and one example of this embodiment will be described below as a ninth embodiment. [Example]

[0067] FIG. 9 is an explanatory diagram showing an example of an optical module 1H according to a ninth embodiment. Note that the same components as those in the optical module 1A according to the second embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. FIG. 9 shows a main part of a holding mechanism 5H provided in the housing 3, and does not show the board 2 on which the optical transmitter 12 and the optical receiver 13 are mounted. The holding mechanism 5H shown in FIG. 9 is mounted in the housing 3 and has a frame-shaped first holding portion 5H1 arranged on one end of the surface of the housing 3, and a frame-shaped second holding portion 5H2 arranged on the other end of the surface of the housing 3.

[0068] The first holding portion 5H1 holds the outer and inner circumferences of one end of the optical fiber 4A having a predetermined radius of curvature. The second holding portion 5H2 holds the outer and inner circumferences of the other end of the optical fiber 4A having a predetermined radius of curvature. The holding mechanism 5H uses the first holding portion 5H1 and the second holding portion 5H2 to hold the bent shape of the optical fiber 4A having a predetermined radius of curvature on the surface of the housing 3.

[0069] That is, the first holding portion 5H1 and the second holding portion 5H2 are arranged at surface positions on the housing 3 that can hold the bent shape of the optical fiber 4A with a predetermined radius of curvature.

[0070] The holding mechanism 5H in the optical module 1H of Example 9 holds one end of the optical fiber 4A from the inner and outer diameters with a first holding portion 5H1 arranged on one end of the housing 3. The holding mechanism 5H holds the other end of the optical fiber 4A from the inner and outer diameters with a second holding portion 5H2 arranged on the other end of the housing 3. The holding mechanism 5H then uses the optical fiber 4A with the first holding portion 5H1 and the second holding portion 5H2 to hold the bent shape of the optical fiber 4A with a predetermined radius of curvature that enables the optical fiber 4A to function as a mode filter. As a result, the bent shape of the optical fiber 4A is maintained, ensuring stable mode filter function. Since a mandrel as in the conventional method is no longer necessary, the module body can be made more compact. Furthermore, because the optical fiber 4A is held by the holding mechanism 5H, the probability of breakage and optical axis misalignment of the optical fiber 4A can be reduced.

[0071] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and one example of this embodiment will be described below as Example 10. [Example]

[0072] FIG. 10 is an explanatory diagram showing an example of an optical module 1J according to a tenth embodiment. The same components as those in the optical module 1 according to the first embodiment are denoted by the same reference numerals, and descriptions of the overlapping components and operations will be omitted. A holding mechanism 5J according to the tenth embodiment differs from the holding mechanism 5 according to the first embodiment in that the optical fiber 4 is held by upper and lower flat surfaces. The holding mechanism 5J includes a first structure 5J1 having a first flat surface 5J11 that abuts the optical fiber 4 from the surface direction of the optical fiber 4, and a second structure 5J2 having a second flat surface 5J21 that abuts the optical fiber 4 from the surface direction of the optical fiber 4 and faces the first flat surface 5J11. The holding mechanism 5J holds the bent shape of the optical fiber 4, which has a predetermined radius of curvature, by sandwiching the optical fiber 4 between the first flat surface 5J11 and the second flat surface 5J21 from the surface direction.

[0073] The first structure 5J1 is mounted on the surface of the substrate 2. Then, an optical fiber 4 having a predetermined radius of curvature is placed on the first flat surface 5J11 of the first structure 5J1. Then, the second flat surface 5J21 of the second structure 5J2 covers the optical fiber 4 from the surface direction. As a result, the holding mechanism 5J holds the bent shape of the optical fiber 4 having a predetermined radius of curvature by sandwiching the optical fiber 4 from the surface direction between the first flat surface 5J11 and the second flat surface 5J21.

[0074] The holding mechanism 5J in the optical module 1J of the tenth embodiment holds the bent shape of the optical fiber 4 with a predetermined radius of curvature by sandwiching the optical fiber 4 between the first flat surface 5J11 and the second flat surface 5J21 from the planar direction. As a result, the holding mechanism 5J holds the bent shape with a predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional case, allowing for a more compact module body. Moreover, because the optical fiber 4 is held by the holding mechanism 5J, the probability of breakage and optical axis misalignment of the optical fiber 4 can be reduced while suppressing stress on the optical fiber 4 itself.

[0075] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and an embodiment of this example will be described below as Example 11. [Example]

[0076] Fig. 11 is an explanatory diagram showing an example of an optical module 1H according to an eleventh embodiment, and Fig. 12 is an explanatory diagram showing an example of a cross section taken along line AA shown in Fig. 11. Note that the same components as those in the optical module 1 according to the first embodiment are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The holding mechanism 5K according to the eleventh embodiment differs from the holding mechanism 5 according to the first embodiment in that the optical fiber 4 is held by forming a bent shape with a predetermined radius of curvature at the top and bottom curved surfaces.

[0077] The holding mechanism 5K has a first structure 5K1 having a first curved surface 5K11 that holds the optical fiber 4K, and a second structure 5K2 that has a second curved surface 5K21 that faces the first curved surface 5K11 and holds the optical fiber 4K. The holding mechanism 5K sandwiches the optical fiber 4K between the first curved surface 5K11 and the second curved surface 5K21, thereby forming and holding the shape of the optical fiber 4K having a predetermined radius of curvature.

[0078] In the optical module 1K of Example 11, the optical fiber 4K is sandwiched between the first curved surface 5K11 and the second curved surface 5K21, thereby maintaining the shape of the optical fiber 4K with a predetermined radius of curvature. As a result, the bent shape of the optical fiber 4K is maintained, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing for a more compact module body. Moreover, because the optical fiber 4K is held by the holding mechanism 5K, the probability of breakage and optical axis misalignment of the optical fiber 4K can be reduced.

[0079] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and one example of this embodiment will be described below as Example 12. [Example]

[0080] Fig. 13 is an explanatory diagram showing an example of an optical module 1L of a twelfth embodiment, and Fig. 14 is an explanatory diagram showing an example of a cross section taken along line BB shown in Fig. 13. Note that the same components as those in the optical module 1 of the first embodiment are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. A holding mechanism 5L of the twelfth embodiment differs from the holding mechanism 5 of the first embodiment in that an inner circumferential surface 5L21 of an insertion hole 5L2 through which the optical fiber 4L is inserted forms a bent shape with a predetermined radius of curvature and holds the optical fiber 4L.

[0081] The holding mechanism 5L has a structure 5L1 with an insertion hole 5L2 that holds the optical fiber 4L when the optical fiber 4L is inserted. When the optical fiber 4L is inserted into the insertion hole 5L2, the holding mechanism 5L forms and holds the shape of the optical fiber 4L having a predetermined radius of curvature on an inner circumferential surface 5L21 of the insertion hole 5L2.

[0082] In the holding mechanism 5L of the optical module 1L of Example 12, the optical fiber 4L is inserted into the insertion hole 5L2 in the structure 5L1, and the optical fiber 4L is held in place by forming a shape of the optical fiber 4L with a predetermined radius of curvature on the inner circumferential surface 5L21 of the insertion hole 5L2. As a result, the bent shape of the optical fiber 4L is formed and held, ensuring stable mode filter function and eliminating the need for a mandrel as in the conventional method, thereby enabling the module body to be made more compact. Moreover, because the optical fiber 4L is held by the holding mechanism 5L, the probability of breakage of the optical fiber 4L and optical axis misalignment can be reduced.

[0083] In the optical module 1 of Example 1, the case where the holding mechanism 5 is mounted on the substrate 2 is exemplified, and one example of this embodiment will be described below as Example 13. [Example]

[0084] 15 is an explanatory diagram showing an example of an optical module 1M according to a thirteenth embodiment. The same components as those in the optical module 1 according to the first embodiment are given the same reference numerals, and explanations of the overlapping components and operations will be omitted. A holding mechanism 5M according to the thirteenth embodiment differs from the holding mechanism 5 according to the first embodiment in that a bent shape of the optical fiber 4M having a predetermined radius of curvature is formed and held using a material 5M1 that changes from a softened state to a hardened state.

[0085] The holding mechanism 5M inserts an optical fiber 4M having a predetermined radius of curvature into a softened material 5M1, hardens the material 5M1, and uses the hardened material 5M1 to hold the shape of the optical fiber 4M having the predetermined radius of curvature.

[0086] In the holding mechanism 5M of the optical module 1M of Example 13, an optical fiber 4M having a predetermined radius of curvature is inserted into a softened material 5M1, and the material 5M1 hardens while the hardened material 5M1 is used to hold the shape of the optical fiber 4M having the predetermined radius of curvature. As a result, the bent shape of the optical fiber 4M is maintained, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing for the miniaturization of the module body. Moreover, because the optical fiber 4M is held by the holding mechanism 5M, the probability of breakage of the optical fiber 4M and optical axis misalignment can be reduced.

[0087] Next, an optical transceiver 50 employing the optical modules of Examples 1 to 13 will be described. FIG. 16 is an explanatory diagram showing an example of the optical transceiver 50 of this example. The optical transceiver 50 shown in FIG. 16 is connected to an optical fiber FC on the transmission path side. The optical transceiver 50 includes a DSP (Digital Signal Processor) 51, an optical transmitter 53, an optical receiver 54, and an optical waveguide mechanism 55. The DSP 51 is an electrical component that performs digital signal processing. For example, the DSP 51 performs processing such as encoding transmission data, generates an electrical signal including the transmission data, and outputs the generated electrical signal to the optical transmitter 53. The DSP 51 also obtains an electrical signal including reception data from the optical receiver 54 and performs processing such as decoding the obtained electrical signal to obtain the reception data.

[0088] The optical transmitter 53 modulates an optical signal with an electrical signal output from the DSP 51, and outputs the resulting transmission light to an optical fiber having a predetermined radius of curvature in the optical waveguide mechanism 55. The optical transmitter 53 has an optical transmitting unit 53A that generates transmission light by modulating the optical signal with an electrical signal input as the optical signal propagates through the optical fiber having a predetermined radius of curvature in the optical waveguide mechanism 55.

[0089] The optical receiver 54 has an optical receiving unit 54A that receives the received light from an optical fiber having a predetermined radius of curvature in the optical waveguide mechanism 55 and demodulates the received light using the light. The optical receiver 54 then converts the demodulated received light into an electrical signal and outputs the converted electrical signal to the DSP 51.

[0090] The optical waveguide mechanism 55 includes a transmission line port 55A that connects to the optical fiber FC, an optical fiber that connects the transmission line port 55A with the optical transmitter 53 and the optical receiver 54 and has a bent shape with a predetermined radius of curvature, and a holding mechanism that holds the bent shape of the optical fiber. The holding mechanism holds the bent shape of the optical fiber with a predetermined radius of curvature, which allows only the fundamental mode of the optical signal that is guided through the optical fiber to propagate. In other words, the bent optical fiber with a predetermined radius of curvature is, for example, the optical fiber with a mode filter function adopted in Examples 1 to 13.

[0091] In the optical transceiver 50 of this embodiment, the optical waveguide mechanism 55 is equipped with a holding mechanism that maintains the bent shape of the optical fiber with a predetermined radius of curvature that enables the mode filter function to be exerted. As a result, the holding mechanism maintains the bent shape with the predetermined radius of curvature, ensuring stable mode filter function and eliminating the need for a mandrel as in the past, allowing for a more compact module body. Moreover, because the optical fiber is held by the holding mechanism, stress on the optical fiber itself is suppressed, while the probability of optical fiber breakage and optical axis misalignment are also suppressed.

[0092] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc. [Explanation of symbols]

[0093] 1 Optical Module 2 boards 3. Housing 4. Optical Fiber 5 Retention mechanism 11 Transmission Line Port 12 Optical transmitter 13 Optical receiver

Claims

1. An optical module comprising: an optical transmitter that outputs transmission light to a transmission line port using an optical signal; an optical receiver that receives reception light from the transmission line port using the optical signal; and an SMF (Single Mode Fiber) optical fiber that connects the optical transmitter and the optical receiver to the transmission line port and through which the optical signal propagates, wherein the wavelength of the optical signal is equal to or shorter than a cutoff wavelength of the optical fiber, a holding mechanism for holding the bent shape of the optical fiber having a predetermined radius of curvature, through which only the fundamental mode of the optical signal is propagated; An optical module comprising:

2. The wavelength of the optical signal is 2. The optical module according to claim 1, wherein the cutoff wavelength is 1.26 [mu]m or less, which is the cutoff wavelength of an SMF optical fiber in the 1.3 [mu]m band.

3. The holding mechanism includes:

3. The optical module according to claim 1, wherein the optical fiber is preformed into a bent shape having the predetermined radius of curvature using thermal stress relaxation, and the bent shape of the optical fiber having the predetermined radius of curvature is maintained.

4. The holding mechanism includes:

3. The optical module according to claim 1, wherein the optical module is arranged on a substrate on which the optical transmitter and the optical receiver are mounted or on a housing on which the substrate is mounted, and maintains the bent shape of the optical fiber having the predetermined radius of curvature.

5. The holding mechanism includes: a first holding portion disposed on one end side of the substrate and holding one end of the optical fiber; a second holding portion disposed on the other end side of the substrate and holding the other end of the optical fiber; 5. The optical module according to claim 4, wherein the first holding portion and the second holding portion are used to hold the shape of the optical fiber having the predetermined radius of curvature.

6. The holding mechanism includes: a first holding portion disposed on one end side of the housing and holding one end of the optical fiber; a second holding portion disposed on the other end side of the housing and holding the other end of the optical fiber, 5. The optical module according to claim 4, wherein the first holding portion and the second holding portion are used to hold the shape of the optical fiber having the predetermined radius of curvature.

7. The holding mechanism includes: a first holding portion having two first struts and holding one end of the optical fiber; a second holding portion having two second struts and holding the other end of the optical fiber; The optical module according to claim 1 or 2, characterized in that the outer and inner circumferences of one end of the optical fiber are held with a portion of the optical fiber sandwiched between two of the first supports, and the outer and inner circumferences of the other end of the optical fiber are held with a portion of the optical fiber sandwiched between two of the second supports, thereby forming and holding the shape of the optical fiber having the predetermined radius of curvature.

8. The holding mechanism includes: a holding groove for holding the optical fiber, the holding groove being provided on a surface of a substrate on which the optical transmitter and the optical receiver are mounted; 3. The optical module according to claim 1, wherein the optical fiber is held in a state where it is laid inside the holding groove, thereby forming and holding the shape of the optical fiber having the predetermined radius of curvature.

9. The holding mechanism includes: a holding groove for holding the optical fiber, the holding groove being provided on a surface of a housing on which a substrate for mounting the optical transmitter and the optical receiver is mounted; 3. The optical module according to claim 1, wherein the optical fiber is held in a state where it is laid inside the holding groove, thereby forming and holding the shape of the optical fiber having the predetermined radius of curvature.

10. The holding mechanism includes: a first structure having a first plane that abuts against the optical fiber from a surface direction of the optical fiber; a second structure that abuts the optical fiber from a surface direction of the optical fiber and has a second plane that faces the first plane, 3. The optical module according to claim 1, wherein the optical fiber is sandwiched between the first plane and the second plane in the planar direction, thereby maintaining the shape of the optical fiber having the predetermined radius of curvature.

11. The holding mechanism includes: a first structure having a first curved surface that holds the optical fiber; a second structure having a second curved surface opposite to the first curved surface, the second structure holding the optical fiber; 3. The optical module according to claim 1, wherein the optical fiber is sandwiched between the first curved surface and the second curved surface to form and hold the shape of the optical fiber having the predetermined radius of curvature.

12. The holding mechanism includes: a structure having an insertion hole for holding the optical fiber in an inserted state; 3. The optical module according to claim 1, wherein the shape of the optical fiber having the predetermined radius of curvature is formed and held on an inner peripheral surface of the insertion hole.

13. The holding mechanism includes:

3. The optical module according to claim 1, wherein a material that changes from a softened state to a hardened state is used, and the material hardens while the optical fiber is inserted into the softened material, thereby maintaining the shape of the optical fiber having the predetermined radius of curvature.

14. an optical transmitter that outputs transmission light to a transmission line port using an electrical signal and an optical signal corresponding to transmission data; an optical receiver that receives reception light from the transmission line port using the optical signal and obtains an electrical signal corresponding to the reception data from the received reception light; a processor that performs signal processing on the electrical signal; and an optical waveguide mechanism that connects the optical transmitter and the optical receiver to the transmission line port and includes an optical fiber of SMF (Single Mode Fiber) through which the optical signal propagates, wherein the wavelength of the optical signal is equal to or shorter than a cutoff wavelength of the optical fiber; The optical waveguide mechanism includes: an optical transceiver comprising a holding mechanism for holding the bent shape of the optical fiber having a predetermined radius of curvature, in which only the fundamental mode of the optical signal is propagated;

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