Optical Monitor Device

Abstract

The present disclosure promotes reduction in size and cost of an optical monitor device for detecting the intensity of light propagating through an optical fiber.　The present disclosure relates to an optical monitor device for detecting the intensity of light propagating through an optical fiber. The optical monitor device is provided with an optical component for splitting, at a specific splitting ratio, and emitting entry light as a part thereof in a first direction and the remainder in a second direction. The optical component is provided with: a single layer film (33) having a uniform thickness; an entry-side member (30A) that is provided to the entry side of the single layer film (33); and an emission-side member (30B) that is provided to the emission side of the single layer film (33). A first refractive index interface (33A) between the single layer film (33) and the entry-side member (30A) and a second refractive index interface (33B) between the single layer film (33) and the emission-side member (30B) are each provided at a specific angle with respect to the optical axis of the entry light. The first direction is a direction of transmission through the first refractive index interface and the second refractive index interface. The second direction is a direction of reflection by the first refractive index interface and the second refractive index interface.

Description

[Technical field]

[0001] The present disclosure relates to an optical monitoring device, and more particularly to an optical monitoring device for detecting the intensity of light in an optical transmission device or the like and feeding back the detection result to other components. [Background technology]

[0002] In recent years, with the increase in Internet traffic, there is a strong demand for increasing communication capacity in communication systems. To achieve this, communication systems using optical fibers are used in the access networks between communication offices and users' homes, and in the core networks connecting communication offices. In optical fiber communication, the detection of the light intensity propagating through the optical fiber is often used to control communication and check the soundness of the equipment. For example, in access networks, test light is propagated through the optical fiber, and the loss and soundness of the optical fiber, as well as the target and connection of the core wires, are confirmed by detecting the light intensity. In addition, WDM (Wavelength Division Multiplexing) transmission used in core networks requires monitoring of the light intensity for feedback control.

[0003] For example, technology such as that described in Patent Document 1 is used for optical power monitoring in access networks. Patent Document 1 describes a technology that splits light at a fixed splitting ratio using two parallel waveguides, which makes it possible to measure the optical signal power and propagation loss in the access network.

[0004] For example, the technology of Patent Document 2 is used for optical intensity monitoring in WMD transmission. Patent Document 2 describes a technology for simultaneously monitoring the intensity of optical signals in multiple optical fibers by combining optical fibers arranged one-dimensionally with a dielectric multilayer film.

[0005] However, the conventional optical monitor device still has the following problems.

[0006] As optical communications become more widespread and the number of optical fiber cores in optical facilities / cables increases, firstly, in the case of optical monitoring devices that use an optical coupler for each optical fiber core, the cost and size increase in proportion to the number of cores.Even in the case of optical monitoring devices in which optical fibers and optical intensity sensors are arranged in a one-dimensional array, there is a limit to the array arrangement of optical fibers, and if the number of optical fiber cores increases, the cost and size increase in proportion to the number of cores.

[0007] As a spatial optical system for constructing such an optical monitor device, for example, Patent Document 2 uses a dielectric multilayer film for optical branching. However, since a dielectric multilayer film generally has a high optical reflectance, there is a problem that the loss of a signal passing through the optical monitor device is large. In addition, since a dielectric multilayer film generally reflects only a specific wavelength band, there is a problem that it is not suitable for monitoring communications that use a wide wavelength band such as WDM transmission. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3450104 (Furukawa Electric) [Patent Document 2] Patent Publication 2004-219523 (Fujitsu, withdrawn) Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present disclosure is to enable monitoring of optical signals in a wide wavelength range in an optical monitoring device for a multi-core optical fiber. [Means for solving the problem]

[0010] In order to achieve the above object, the optical monitor device of the present disclosure comprises: An optical monitor device for detecting the intensity of light propagating through a plurality of optical fibers, comprising: an optical component that splits a part of incident light into a first direction and the rest into a second direction at a specific split ratio and outputs the split light; The optical component is A monolayer film having a uniform thickness; an incident side member provided on an incident side of the monolayer film and having a refractive index different from that of the monolayer film; an exit side member provided on the exit side of the single layer film and having the same refractive index as the entrance side member; Equipped with a first refractive index interface between the monolayer film and the incident-side member and a second refractive index interface between the monolayer film and the output-side member are provided at specific angles with respect to an optical axis of the incident light, the first direction is a direction passing through the first refractive index interface and the second refractive index interface, The second direction is a direction in which light is reflected at the first refractive index interface and the second refractive index interface. Effect of the Invention

[0011] The optical monitoring device of the present disclosure is an optical monitoring device that detects the intensity of light propagating through multiple optical fibers, and splits incident light using a single-layer film having a uniform thickness. Since the optical monitoring device of the present disclosure splits incident light using a single-layer film, optical signals in a wide wavelength range can be monitored. Therefore, according to the present disclosure, an optical monitoring device for optical fibers with a large number of cores can monitor optical signals in a wide wavelength range. [Brief description of the drawings]

[0012] [Figure 1] 1 illustrates an example embodiment of an optical monitor device of the present disclosure. [Diagram 2] 1 shows an example of light propagating through a spatial optical system. [Diagram 3] 1 illustrates an example embodiment of an optical monitor device of the present disclosure. [Figure 4] 1 shows an example of a light path in a single layer film. [Diagram 5] An example of a branching ratio in a spatial optical system is shown. [Figure 6]An example of the relationship between the minimum branching ratio and the ratio of the thickness of the single layer film to the beam radius is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings are assumed to indicate the same components.

[0014] (First embodiment) The optical monitoring device of this embodiment has a configuration exemplified in FIG. The optical monitoring device of this embodiment is an optical monitoring device that detects the intensity of light propagating through a plurality of incident side optical fibers 11, a spatial optical system (30) for splitting a majority of the incident light (41) from an incident-side optical fiber (11) in a specific first direction and the remainder in another specific second direction at a constant split ratio, and emitting each split light; a plurality of incident-side optical fibers 11 for propagating light, the optical fibers being arranged in a two-dimensional array so as to introduce light into the spatial optical system 30; an output-side optical fiber 12 for propagating a plurality of beams, the output-side optical fiber 12 being disposed so as to receive most of the output beam 42 outputted in a first direction from the spatial optical system 30; a light receiving unit 5 arranged to receive a portion of the emitted light 43 emitted in a second direction from the spatial optical system 30; an incident-side optical lens 21 disposed between the spatial optical system 30 and the incident-side optical fiber 11, for converting each incident light from the incident-side optical fiber 11 to the spatial optical system 30 into a parallel light; an output optical lens 22 that is disposed between the spatial optical system 30 and the output-side optical fiber 12 and efficiently couples each output light from the spatial optical system 30 to the output-side optical fiber 12 corresponding to the input-side optical fiber 11; has.

[0015] 2, the spatial optical system 30 includes a monolayer film 33 having a uniform refractive index provided between an incident side member 30A and an exit side member 30B made of a material having a uniform refractive index, and the monolayer film 33 is provided at a specific angle (45 degrees in the figure) with the optical axis of the incident light 41. As a result, a first refractive index interface 33A between the monolayer film 33 and the incident side member 30A and a second refractive index interface 33B between the monolayer film 33 and the exit side member 30B are each provided at a specific angle with the optical axis of the incident light.

[0016] 1 shows an example in which the specific angle is 45 degrees and the direction of the reflected light is 90 degrees, but the direction of the reflected light is not fixed at 90 degrees and can be changed as necessary. In addition, the spatial optical system 30 is not limited to a spatial system, and any optical component having a branching surface capable of branching into two lights with different directions can be used.

[0017] 1 and 2, the incident light 41 from the incident-side optical fiber 11 becomes parallel light at the incident-side optical lens 21, thereby preventing loss due to diffusion. Furthermore, most of the emitted light 42 is guided to the output-side optical lens 22 by the spatial optical system 30. The output-side optical lens 22 collects the light that has passed through the spatial optical system 30 and couples it to the output-side optical fiber 12. In this way, most of the emitted light 42 emitted from the incident-side optical fiber 11 can be guided to the output-side optical fiber 12 with little loss.

[0018] On the other hand, a part of the output light 43 branched by the spatial optical system 30 is guided to the light receiving unit 5 arranged in a different direction from the majority of the output light 42. As a result, the optical monitor device of this embodiment can measure the intensity of a part of the light propagating from the incident side optical fiber 11 to the output side optical fiber 12. If the branching ratio between the output light 42 and the output light 43 in the spatial optical system 30 is constant and known in advance, for example, N:1, and the intensity of the light measured by the light receiving unit 5 is L (for example, in mW), it can be known that the intensity of the light incident from the incident side optical fiber 11 is (N+1)×L, and the intensity of the light propagating to the output side optical fiber 12 is N×L.

[0019] The light receiving unit 5 may be composed of a plurality of light receiving elements arranged to match the two-dimensional array shape of the incident side optical fibers 11, or may be composed of a single light receiving element capable of detecting the light intensity for each incident position from each incident side optical fiber 11, such as an area image sensor. In this case, the intensity of each output light 43 detected by the light receiving unit 5 is output for each incident side optical fiber 11. This allows the number of parts to be reduced, and allows use with incident side optical fibers 11 in any two-dimensional array.

[0020] 1 and 2, incident light is branched by Fresnel reflection at the refractive index interfaces 33A and 33B. Since Fresnel reflection does not depend on wavelength but on the refractive index at the refractive index interfaces 33A and 33B, light is branched in a wide wavelength range.

[0021] 2 illustrates the difference in optical path depending on the wavelength of incident light when the incident side member 30A and the exit side member 30B have the same refractive index. When the incident side member 30A and the exit side member 30B have the same refractive index, different wavelengths travel in different directions in the single-layer film 33. Therefore, the incident position on the refractive index interface 33B differs depending on the wavelength. On the other hand, light incident from the refractive index interface 33B travels in the same direction as the incident side member 30A due to refraction between the single-layer film 33 and the exit side member 30B. Therefore, even if the optical axes at the entrance end faces of the exit side optical fibers 12 are arranged in parallel, the transmitted light can be coupled to the exit side optical fiber 12 regardless of the wavelength.

[0022] In this manner, in the present disclosure, the position of incidence on the refractive index interface 33B varies depending on the wavelength in the single layer film 33. For this reason, in the present disclosure, the position of the output side optical lens 22 is determined depending on the central wavelength and refraction angle of the incident light 41 and the thickness S of the single layer film 33.

[0023] Furthermore, the width of the light reaching the output optical lens 22 mainly depends on the wavelength width of the incident light 41 and the thickness S of the single-layer film 33. If the width of the light reaching the output optical lens 22 is small relative to the diameter of the output optical lens 22, the light loss is small, whereas if this width is large, the light loss is large. Therefore, the light loss can be reduced by setting the diameter of the output optical lens 22 to a value or more determined according to the wavelength width of the incident light 41 and the thickness S of the single-layer film 33. On the other hand, if the diameter of the output optical lens 22 is greater than or equal to the installation interval of the input fiber, the lens 22 will collide with an adjacent lens, and therefore the diameter of the output optical lens 22 must be less than or equal to the installation interval of the input fiber.

[0024] (Effects of the present disclosure) According to the optical monitoring device illustrated in FIG. 1, the input optical fiber 11 and the output optical fiber 12 are arranged two-dimensionally, and the two-dimensionally arranged light beam is split by the spatial optical system 30. This has the effect of making it possible to reduce the size compared to using an optical monitoring device for each single optical fiber or an optical monitoring device in which optical fibers are arranged one-dimensionally. In addition, since the number of components is small, it is easy to reduce costs. In addition, since light is split in a wide wavelength range, it is possible to monitor optical signals in a wider wavelength range than optical monitoring devices using a dielectric multilayer film. Therefore, the optical monitoring device disclosed herein can monitor optical signals in a wide wavelength range, and can realize an optical monitoring device for optical fibers with a large number of cores, such as tens of cores, at a small size and low cost.

[0025] Although FIG. 1 shows an example in which the incident side optical fiber 11, the exit side optical fiber 12, the incident side optical lens 21, and the exit side optical lens 22 are arranged in a 3×3 two-dimensional array, any number of combinations equal to or greater than 2×2 may be used.

[0026] Second embodiment FIG. 3 shows an example of the configuration of the optical monitor device according to this embodiment. The incident side member 30A and the exit side member 30B can be made of a transparent material such as quartz glass. The single layer film 33 can be formed by placing a spacer 34 of a predetermined thickness between the incident side member 30A and the exit side member 30B and opening a gap to utilize an air layer. The incident side optical lens 21 and the exit side optical lens 22 can be realized by a collimator in which a GRIN (GRaded INdex) fiber is built into a rectangular ferrule used in optical connectors and the like. The incident side optical fiber 11 and the exit side optical fiber 12 are also built into rectangular ferrules 23 and 24, similar to the incident side optical lens 21 and the exit side optical lens 22, and the optical axes of the incident side optical fiber 11, the incident side optical lens 21, the exit side optical fiber 12, and the exit side optical lens 22 can be aligned using a guide pin 25 and a guide hole, similar to an optical connector. The light receiving unit 5 can be realized by a commercially available optical image sensor. By filling the connecting portion other than the single layer film 33 with a refractive index matching material, unnecessary Fresnel reflection can be suppressed.

[0027] In addition, in order to suppress unnecessary Fresnel reflection, it is desirable that the refractive index of the incident side member 30A and the exit side member 30B is equivalent to that of the optical fiber core of the incident side optical fiber 11 and the exit side optical fiber 12. For example, if the incident side optical fiber 11 and the exit side optical fiber 12 are fiber cores made of silica glass used in communication optical fibers, it is desirable to use a refractive index matching material with a refractive index of 1.47. It can be said that an inexpensive structure is to use an air layer (refractive index 1) for the single layer film 33. If the incident angle to the single layer film 33 is 30 degrees, the Fresnel reflectance (p-polarized light) is 8.5%.

[0028] FIG. 4 illustrates a detailed example of the transmitted light and reflected light in the single-layer film 33. If the intensity of the incident light 41 entering the spatial optical system 30 from the incident side optical fiber 11 is L0, the intensities of the first reflected light, the second reflected light, and the third reflected light are L R1 , L R2 , L R3 are expressed by the following formulas, respectively.

number

[0029] Here, r1 is the Fresnel reflectance at the refractive index interface 33A, and r2 is the Fresnel reflectance at the refractive index interface 33B. Furthermore, δ is the phase of the light that has traveled through the single layer film 33, and is 4πnScosθ / λ. Here, n is the refractive index of the single layer film 33, S is the thickness of the single layer film 33, θ is the refraction angle, and λ is the wavelength of the light. In this embodiment, since the single layer film 33 is an air layer, the refractive index n=1. Furthermore, in FIG. 4, the intensities L of the first transmitted light, second transmitted light, and third transmitted light are T1 , L T2 , L T3 Shows.

[0030] Furthermore, if the incident light 41 is converted into a parallel light beam with a light beam radius R by the incident-side optical lens 21, the overlap integral of the i-th reflected light and the j-th reflected light is expressed by the following equation.

number

number

[0031] If we ignore the reflected light of fourth and higher orders because they are minute, the intensity L of the light reflected by the spatial optical system 30 and received by the light receiving unit 5 is expressed by the following equation.

number

[0032] Figure 5 shows the relationship between the minimum branching ratio and the ratio of the thickness S of the single layer film 33 to the light beam radius R. The minimum optical signal strength of an optical communication device is internationally standardized, for example, in IEC 61753-1, and is approximately -20 to -25 dB. On the other hand, the minimum light receiving sensitivity of an optical sensor is generally -40 dB, so a branching ratio of -15 dB or more is required to be usable in a wide range of devices. To achieve this, it can be seen from Figure 5 that the thickness S of the single layer film 33 is required to provide an S / R of 0.5 or more.

[0033] FIG. 6 shows the branching ratio in the spatial optical system 30 when the ratio of the thickness S of the single layer film 33 to the beam radius R is changed. It can be seen that light can be branched in a wide wavelength range in all cases of S / R=0.5, 2.0, and 4.0. However, when the ratio of S to R is 0.5, a wavelength range with a small branching ratio appears due to interference in the spatial optical system 30. Thus, interference occurs in the spatial optical system 30 depending on the combination of the thickness S of the single layer film 33 and the beam radius R. Therefore, it is preferable to set the thickness S of the single layer film 33 such that the ratio of S to R is 0.5 or more, and the beam radius R to avoid interference in the single layer film 33.

[0034] The above are examples, but the present disclosure is not limited to these. For example, the single layer film 33 is an air layer, but the single layer film 33 may be glass having a lower refractive index than the incident side member 30A and the exit side member 30B. The spatial optical system 30 is not limited to a cubic shape, and may be any shape such as a rectangular parallelepiped. The light receiving unit 5 may be disposed at any position where the light branched by the spatial optical system 30 can be received. For example, the light receiving unit 5 may be embedded inside the spatial optical system 30.

[0035] The optical monitoring device of the present disclosure can be used to monitor any light transmitted in an optical transmission system. For example, the optical monitoring device of the present disclosure can be mounted in any device used in an optical transmission system, such as a transmitting device, a receiving device, or a repeater, and the measurement result at the light receiving unit 5 can be used for feedback or feedforward to any component inside or outside the device. Also, the optical monitoring device of the present disclosure can be inserted in the middle of a transmission line in an optical transmission system to measure the intensity and propagation loss of an optical signal in the transmission line. [Industrial Applicability]

[0036] The present disclosure can be applied to the information and communications industry. [Explanation of symbols]

[0037] 5: Light receiving part 11: Input optical fiber 12: Output optical fiber 21: Input optical lens 22: Output optical lens 23, 24: Ferrule 25: Guide pin 30: Spatial optical system 30A:Incidence side member 30B: Output side member 33: Single layer membrane 34: Spacer 41: Incident light 42: Most of the light emitted 43: Part of the emitted light

Claims

1. 1. An optical monitor device for detecting the intensity of optical signals propagating through a plurality of optical fibers, comprising: an optical component that splits a part of the optical signal in a first direction and the rest in a second direction at a specific splitting ratio and outputs the split signal; a plurality of incident side optical fibers arranged in a two-dimensional array so as to input the optical signal to the optical component; a plurality of output side optical fibers arranged in a two-dimensional array so as to receive each output light from the optical component in the first direction; a light receiving unit arranged to receive each of the light beams emitted from the optical component in the second direction; an incident-side optical lens disposed between the optical component and the incident-side optical fiber, and converting the optical signals from the plurality of incident-side optical fibers into parallel light; an output optical lens disposed between the optical component and the output optical fiber, for coupling each output light from the optical component to the output optical fiber; Equipped with the optical signal is wavelength multiplexed; The optical component is a monolayer having a uniform thickness that branches in the second direction by a constant value of less than 14%; an incident side member provided on an incident side of the monolayer film and having a refractive index different from that of the monolayer film; an exit side member provided on the exit side of the single layer film and having the same refractive index as the entrance side member; Equipped with a first refractive index interface between the single layer film and the incident side member and a second refractive index interface between the single layer film and the exit side member are provided at specific angles with respect to an optical axis of the optical signal, the first direction is a direction passing through the first refractive index interface and the second refractive index interface, the second direction is a direction of reflection at the first refractive index interface and the second refractive index interface, the monolayer film has a thickness S such that a ratio of the thickness S of the monolayer film to a light beam radius R of the parallel light emitted from the incident side optical lens is 0.5 or more; The light beam radius is such that interference in the single layer film can be avoided. Optical monitor device.

2. The incident side member and the exit side member are transparent bodies having the same refractive index.

2. The optical monitor device according to claim 1 .

3. An optical monitor device for detecting the intensity of optical signals propagating through a plurality of optical fibers, comprising: an optical component that splits a part of the optical signal in a first direction and the rest in a second direction at a specific splitting ratio and outputs the split signal; a light receiving unit that receives the optical signal branched in the second direction from the optical component; Equipped with the optical signal is wavelength multiplexed; The optical component is a monolayer having a uniform thickness that branches in the second direction by a constant value of less than 14%; an incident side member provided on an incident side of the monolayer film and having a refractive index different from that of the monolayer film; an exit side member provided on the exit side of the single layer film and having the same refractive index as the entrance side member; Equipped with a first refractive index interface between the single layer film and the incident side member and a second refractive index interface between the single layer film and the exit side member are provided at specific angles with respect to an optical axis of the optical signal, the first direction is a direction passing through the first refractive index interface and the second refractive index interface, the second direction is a direction of reflection at the first refractive index interface and the second refractive index interface, the incident side member and the exit side member are made of quartz glass having the same refractive index, The single layer film is an air layer or a transparent glass having a lower refractive index than the incident side member and the exit side member. Optical monitor device.

4. The position of the output optical lens is determined according to the central wavelength of the optical signal.

2. The optical monitor device according to claim 1 .

5. a diameter of the output optical lens is equal to or larger than a value determined according to a wavelength width of the optical signal and is equal to or smaller than an installation interval of the input optical fibers; 2. The optical monitor device according to claim 1 .

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