Optical communication device and optical fiber state detection method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NT T INC
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-02
Smart Images
Figure JP2024045953_02072026_PF_FP_ABST
Abstract
Description
Optical communication device and optical fiber status detection method
[0001] The present invention relates to an optical communication device and a method for detecting the state of an optical fiber.
[0002] Conventionally, a method has been proposed in which power is supplied simultaneously with data transmission via an optical fiber that transmits optical signals, using an optical power supply method. As a method for detecting breaks in the optical fiber used in such a method, the method shown in Figures 14 and 15 has been proposed. Figures 14 and 15 are diagrams (part 1) illustrating a method for detecting breaks in an optical fiber in a conventional optical communication system S. As shown in Figures 14 and 15, optical communication device 1 and optical communication device 2 are connected by an optical fiber F. Optical communication device 1 includes a light source 3, a circulator 4, and a reflected light measuring unit 5. The power supply light emitted from the light source 3 of optical communication device 1 is output to the optical fiber F by the circulator 4.
[0003] The optical communication device 2 converts the power supply light emitted from the light source 3 of the optical communication device 1 into electricity using the PD 6 and stores it in the storage battery 7. The optical communication device 2 then operates solely on the power stored in the storage battery 7. Therefore, the optical communication device 2 has a limited amount of usable power. In the configuration shown in Figures 14 and 15, the optical communication device 1 measures the intensity of the reflected light from the optical fiber F using the reflected light measuring unit 5. The optical communication device 1 then detects the breakage of the optical fiber F based on the measurement result of the reflected light intensity by the reflected light measuring unit 5.
[0004] For example, if no break occurs in the optical fiber F, the amount of reflection will be almost zero, as shown in Figure 14. On the other hand, if a break occurs in the optical fiber F, the amount of reflection will increase, as shown in Figure 15. Therefore, the optical communication device 1 detects that a break has occurred in the optical fiber F when the measurement result of the reflected light intensity by the reflected light measurement unit 5 becomes high (for example, when the measurement result of the reflected light intensity exceeds a predetermined threshold).
[0005] In this method, depending on the cross-sectional shape of the optical fiber F, a large amount of light may leak out of the fiber from the cross-section, resulting in a very small amount of reflection at the cross-section. In this case, the measurement result by the reflected light measurement unit 5 will be low (for example, the measurement result of the intensity of the reflected light will be below a predetermined threshold), leading to the problem of not being able to detect the breakage of the optical fiber F. In particular, in optical power supply, high-intensity light is generally input to the fiber, so from the perspective of safety for the surrounding area of the fiber, it is necessary to detect the breakage of the optical fiber F with high precision and stop the light input. However, the above method has low accuracy in detecting the breakage of the optical fiber F.
[0006] As a method for detecting breaks in optical fibers, the method shown in Figures 16 and 17 has also been proposed. Figures 16 and 17 are diagrams (part 2) illustrating a method for detecting breaks in optical fibers in a conventional optical communication system Sa. In the method shown in Figures 16 and 17, the optical communication device 2a (the side receiving optical power) is equipped with a light source 9, and the light source 9 constantly emits a liveness monitoring signal (or a similar signal). The liveness monitoring signal (or a similar signal) emitted from the light source 9 is output to the optical fiber F via the circulator 8. The circulator 8 also outputs the power supply light emitted from the optical communication device 1 to the PD 6. The optical communication device 1 detects the break of the optical fiber F based on the measurement result of the intensity of the liveness monitoring signal (or a similar signal) by the reflected light measuring unit 5.
[0007] For example, if no break occurs in the optical fiber F, the liveness monitoring signal (or a similar signal) sent from the light source 9 reaches the optical communication device 1, and as shown in Figure 16, the intensity of the liveness monitoring signal (or a similar signal) becomes a predetermined amount. On the other hand, if a break occurs in the optical fiber F, there is a high possibility that the liveness monitoring signal (or a similar signal) sent from the light source 9 will not reach the optical communication device 1 (or even if it does reach it, the intensity will be low), and as shown in Figure 17, the intensity of the liveness monitoring signal (or a similar signal) will be a value different from the predetermined amount. In this way, the optical communication device 1 detects that a break has occurred in the optical fiber F when the measurement result of the reflected light intensity by the reflected light measurement unit 5 differs from the predetermined amount.
[0008] However, this method requires that the device receiving optical power (for example, the optical communication device 2a) be equipped with a light source 9 or an optical transceiver and output a status monitoring signal to the optical communication device 1. Therefore, there is a problem that the optical communication device 2 consumes a large amount of power to drive the light source 9 or optical transceiver. In general, with optical power supply, the amount of power available on the optical communication device 2 side is very small compared to commercial power supply. This is because optical power supply transmits high-intensity light (to the extent permitted from a safety standpoint) from the optical communication device 1 installed in the central office, and even if this light reaches the optical communication device 2 while maintaining its high intensity, converting this light into electricity yields only a small amount of power, ranging from a few mW to several hundred mW. Therefore, it is desirable that the mechanism for detecting the breakage of the optical fiber F be very power-efficient.
[0009] Hiroaki Kubozono, "Everything You Need to Know! Fiber Optic Communication," Part III, Chapter 3.3.1 (P232), published in 2012.
[0010] As described above, conventional methods for detecting the breakage of optical fiber F have the problem of not being able to detect the breakage of optical fiber F with high accuracy while keeping the power consumption of the optical communication equipment (for example, the power consumption of optical communication equipment receiving optical power) low. Here, we have explained using the breakage of optical fiber F as an example, but this problem can also occur when detecting the condition of optical fiber F (for example, a faulty connector connection). Furthermore, although the above example was explained using an optical communication system that provides optical power, this problem can also occur in a general optical communication system that connects optical communication equipment using optical fiber F.
[0011] In view of the above circumstances, the present invention aims to provide a technology that can detect the state of an optical fiber with high accuracy while reducing the power consumption of an optical communication device.
[0012] One aspect of the present invention is an optical communication device comprising a reflected light generation unit that uses light emitted from an optical communication device to be communicated, connected via an optical fiber, to generate reflected light having a specific waveform pattern for detecting the state of the optical fiber, and sends the generated reflected light to the optical communication device to be communicated.
[0013] One aspect of the present invention is an optical fiber state detection method, which involves using light emitted from an optical communication device to be communicated via an optical fiber to generate reflected light having a specific waveform pattern for detecting the state of the optical fiber, sending the generated reflected light to the optical communication device to be communicated, and the optical communication device to be communicated detecting the state of the optical fiber based on the reflected light.
[0014] This invention makes it possible to detect the state of an optical fiber with high precision while reducing the power consumption of the optical communication device.
[0015] This is a diagram illustrating the outline of the present invention. This is a diagram illustrating the outline of the present invention. This is a diagram illustrating an example configuration of an optical communication system in the first embodiment. This is a diagram illustrating an example of a waveform pattern generated by the reflected light generation unit. This is a diagram illustrating an example configuration of the reflected light generation unit. This is a diagram illustrating an example configuration of the reflected light generation unit. This is a sequence diagram showing the processing flow of the optical communication system in the first embodiment. This is a diagram illustrating an example configuration of an optical communication system in the second embodiment. This is a diagram illustrating an example configuration of an optical communication system in the third embodiment. This is a diagram illustrating the processing of reflected light generation in the third embodiment. This is a diagram illustrating an example configuration of an optical communication system in the fourth embodiment. This is a diagram illustrating another example of a reflected light generation unit. This is a diagram illustrating an example of an arbitrary waveform generated by another example of a reflected light generation unit. This is a diagram (1) illustrating a method for detecting a break in an optical fiber in a conventional optical communication system. This is a diagram (1) illustrating a method for detecting a break in an optical fiber in a conventional optical communication system. This is a diagram (2) illustrating a method for detecting a break in an optical fiber in a conventional optical communication system. This is a diagram (2) illustrating a method for detecting a break in an optical fiber in a conventional optical communication system.
[0016] One embodiment of the present invention will be described below with reference to the drawings.
[0017] (Overview) Before describing the specific configuration of the present invention, the overview of the invention will be explained first. Figures 1 and 2 are diagrams illustrating the overview of the present invention. The present invention enables high-precision and low-power detection of the state of an optical fiber F in an optical communication system in which an optical communication device 10 and one or more optical communication devices 20 are connected by an optical fiber F. The state of the optical fiber F includes, for example, one or more of the following: breakage of the optical fiber F, connector connection failure, dirt on the end face of the optical fiber F, or bending of the optical fiber F. In the following description, an optical power supply system that supplies optical power from the optical communication device 10 to the optical communication device 20 will be used as an example of an optical communication system, but the present invention is applicable to a general optical communication system that connects the optical communication device 10 and the optical communication device 20 using an optical fiber F.
[0018] The optical communication device 10 transmits optical signals to the optical communication device 20. For example, the optical communication device 10 is installed in a central office building and transmits optical signals (power supply light) to the optical communication device 20 to provide optical power. Furthermore, the optical communication device 10 transmits and receives data with the optical communication device 20.
[0019] The optical communication device 20 receives optical signals transmitted from the optical communication device 10. For example, the optical communication device 20 is powered by the power obtained from the power supply light transmitted from the optical communication device 10. Since the power supply light generally has a higher light intensity compared to PON (Passive Optical Network), etc., the amount of reflected light is also large. Therefore, the optical communication device 20 uses the power supply light transmitted from the optical communication device 10 to generate reflected light with a specific waveform pattern. The specific waveform pattern will be described later. The optical communication device 20 outputs the generated reflected light to the optical communication device 10.
[0020] As described above, the reflected light generated by the optical communication device 20 is input to the optical communication device 10 via the optical fiber F. Therefore, if there is no abnormality in the condition of the optical fiber F (for example, no abnormality such as breakage of the optical fiber F), reflected light with a specific waveform pattern will always reach the optical communication device 10, as shown in Figure 1. Therefore, the optical communication device 10 can determine that there is no abnormality in the condition of the optical fiber F as long as the specific waveform pattern is being measured. The specific waveform pattern generated by the optical communication device 20 is predetermined between the optical communication device 10 and the optical communication device 20.
[0021] On the other hand, if an abnormality occurs in the condition of the optical fiber F (for example, if the optical fiber F breaks), reflected light with a specific waveform pattern will no longer reach the optical communication device 10, as shown in Figure 2. Therefore, the optical communication device 10 can determine that an abnormality has occurred in the condition of the optical fiber F when the specific waveform pattern is no longer measured.
[0022] As described above, in the present invention, the optical communication device 10, which is the transmitting side of the optical signal (for example, the transmitting side of the power supply light), detects the state of the optical fiber F according to whether or not reflected light (optical signal) with a specific waveform pattern is measured. As described above, the reflected light with a specific waveform pattern utilizes the optical signal transmitted from the optical communication device 10, so there is no need to newly provide a light source in the optical communication device 20. Furthermore, since the optical communication device 10 detects the state of the optical fiber F according to whether or not reflected light with a specific waveform pattern has been measured, it becomes possible to detect the state regardless of the amount of reflection, as in the conventional method. Therefore, it becomes possible to detect the state of the optical fiber with high accuracy while suppressing the power consumption of the optical communication device. The specific configuration for realizing the above process will be described below.
[0023] (First Embodiment) Figure 3 shows an example of the configuration of the optical communication system 100 in the first embodiment. The optical communication system 100 comprises one optical communication device 10 and one optical communication device 20. The optical communication device 10 and the optical communication device 20 are connected by an optical fiber F. The functions of the optical communication device 10 and the optical communication device 20 have been described above, so the specific configuration of the optical communication device 10 and the optical communication device 20 will now be described.
[0024] (Configuration of Optical Communication Device 10) First, the configuration of the optical communication device 10 will be explained. The optical communication device 10 comprises a light source 11, a circulator 12, and a reflected light measuring unit 13. The light source 11 outputs light of a specific wavelength or a specific wavelength range. For example, the light source 11 outputs light of a certain wavelength as power supply light to supply power to the optical communication device 20.
[0025] The circulator 12 has at least three ports. In the following description, it is assumed that the circulator 12 has three ports. The first port 121 of the circulator 12 is connected to the light source 11. The second port 122 of the circulator 12 is connected to the optical fiber F which is connected to the reflected light generation unit 21 in the optical communication device 20. The third port 123 of the circulator 12 is connected to the reflected light measurement unit 13. The optical signal (power supply light) input to the first port 121 of the circulator 12 is output from the second port 122. The optical signal input to the second port 122 of the circulator 12 is output from the third port 123. The optical signal input to the third port 123 of the circulator 12 is output from the first port 121.
[0026] The reflected light measuring unit 13 receives an optical signal output from the third port 123 of the circulator 12. The optical signal input to the reflected light measuring unit 13 is an optical signal generated by the optical communication device 20 using power supply light. The reflected light measuring unit 13 measures the input optical signal. The reflected light measuring unit 13 determines that there is no abnormality in the optical fiber F if the waveform obtained as a result of the measurement has a predetermined specific waveform pattern. The reflected light measuring unit 13 determines that there is an abnormality in the optical fiber F if an optical signal is not obtained within a predetermined time from the output of light from the light source 11, or if the waveform obtained as a result of the measurement does not have a predetermined specific waveform pattern.
[0027] (Configuration of the optical communication device 20) Next, the configuration of the optical communication device 20 will be described. The optical communication device 20 includes a reflected light generation unit 21, a PD 22, a storage battery 23, and a control unit 24. The light source 11 outputs light of a specific wavelength. For example, the light source 11 outputs light of a certain wavelength as power supply light to supply power to the optical communication device 20.
[0028] The reflected light generation unit 21 generates reflected light with a specific waveform pattern using light transmitted from the optical communication device 10. In this process, the reflected light generation unit 21 generates reflected light with a specific waveform pattern by operating in accordance with instructions from the control unit 24. Since optical power supply requires a small amount of power, it is desirable that the reflected light generation unit 21 consume little power. Therefore, it is desirable that the reflected light generation unit 21 be composed of, for example, a mechanical optical switch or a MEMS (Micro Electro Mechanical Systems) optical switch. This allows the optical communication device 20 to directly reflect a portion of the light received by optical power supply, resulting in a power-saving configuration. Note that the optical switch is not limited to the above-mentioned type; other optical switches capable of dynamically switching the optical path may also be used.
[0029] PD22 is a photoelectric conversion unit that converts the power supply light emitted from the optical communication device 10 into electrical power. More specifically, PD22 converts the light that has passed through the reflected light generation unit 21 from the power supply light emitted from the optical communication device 10 into electrical power. The storage battery 23 stores the electrical power converted by PD22. The optical communication device 20 is powered by the electrical power stored in the storage battery 23.
[0030] The control unit 24 controls the operation of the reflected light generation unit 21. For example, the control unit 24 controls the waveform pattern generated by the reflected light generation unit 21. In this way, the control unit 24 controls the operation of the reflected light generation unit 21 so that it generates a waveform pattern predetermined in relation to the optical communication device 10. The reflected light generation unit 21 and the control unit 24 operate using power obtained from, for example, the storage battery 23.
[0031] (Waveform Pattern) Next, the waveform patterns generated by the reflected light generation unit 21 will be explained using Figure 4. Figure 4 is a diagram showing an example of a waveform pattern generated by the reflected light generation unit 21. Six waveform patterns are shown as examples in Figure 4. Note that the waveform patterns generated by the reflected light generation unit 21 are not limited to these, but some examples are shown in Figure 4 for clarity.
[0032] The waveform pattern generated by the reflected light generation unit 21 may be a waveform with constant intensity as shown in Figure 4(A), an intensity-modulated waveform as shown in Figure 4(B), an ON / OFF-modulated waveform as shown in Figure 4(C), a sine wave (or cosine wave (not shown)) with a constant frequency as shown in Figure 4(D), the upper half of a sine wave (or cosine wave (not shown)) as shown in Figure 4(E), or an irregular waveform as shown in Figure 4(F).
[0033] In addition, the waveform pattern generated by the reflected light generation unit 21 may be a digital or analog FM (Frequency Modulation) modulated waveform, a digital or analog PM (Phase Modulation) modulated waveform, or any other waveform that is mathematically known. Any waveform is acceptable as long as it is a waveform that can be generated by the reflected light generation unit 21 and is predetermined between the optical communication device 10 and the optical communication device 20.
[0034] Next, the specific processing of the reflected light generation unit 21 will be explained using Figures 5 and 6. Figures 5 and 6 show examples of the configuration of the reflected light generation unit 21. In Figures 5 and 6, an example is shown in which a mechanical optical switch is used as the reflected light generation unit 21, in which case the control unit 24 controls the movable part of the mechanical optical switch.
[0035] The reflected light generation unit 21 includes an input port 211, a plurality of output ports 212, and a switching unit 213. In Figures 5 and 6, the reflected light generation unit 21 has two output ports 212, but the number of output ports 212 is not particularly limited. The input port 211 is a port into which light (power supply light) transmitted from the optical communication device 10 is input. That is, the input port 211 is connected to an optical fiber F connected to the optical communication device 10. Each output port 212-1, 212-2 is a port that outputs the power supply light input to the input port 211. At least one of each output port 212-1, 212-2 is connected to a PD 22. Therefore, the PD 22 takes the power supply light output from the connected output port 212 as input. Although Figure 3 shows a configuration in which the optical communication device 20 has one PD22, to achieve the above, the optical communication device 20 may have a number of PD22s that corresponds to the number of output ports of the reflected light generation unit 21 (for example, if the number of output ports of the reflected light generation unit 21 is two, then the number of PD22s may also be two). Alternatively, the optical communication device 20 may have a number of input ports for the PD22s that corresponds to the number of output ports of the reflected light generation unit 21 (for example, if the number of output ports of the reflected light generation unit 21 is two, then the number of input ports for the PD22s may also be two).
[0036] The switching unit 213 controls the output destination of the power supply light input to the input port 211 in accordance with instructions from the control unit 24. The switching unit 213 is composed of a plurality of lenses 214 and a prism 215. A lens 214 is provided for each port and converts the input light (power supply light) into a parallel beam or focuses it. The lens 214 is, for example, a green lens. The prism 215 reflects the input light (power supply light) and outputs it to the desired output port 212. The prism 215 can be moved in parallel. By moving the prism 215 in parallel, the output destination of the power supply light can be switched between output port 212-1 and output port 212-2.
[0037] Furthermore, the design method for the amount of reflection for each path can be defined, for example, by the number of fusion points. For example, if there are no fusion points P, there is less reflected light, and if there are fusion points P, there is more reflected light. Figures 5 and 6 show the case where output port 212-1 has no fusion points P, and output port 212-2 has fusion points P. As a result, output port 212-2 has more reflected light than output port 212-1.
[0038] The control unit 24 controls the position of the prism 215 according to the waveform pattern generated by the reflected light generation unit 21. This causes the reflected light generation unit 21 to generate a specific waveform pattern. For example, if the control unit 24 causes the reflected light generation unit 21 to generate a waveform with constant intensity as a specific waveform pattern, as shown in Figure 4(A), the control unit 24 always controls the position of the prism 215 so that light is input to output port 212-1, which does not have a fusion point P, as shown in Figure 6. Alternatively, although not shown, the control unit 24 always controls the position of the prism 215 so that light is input to output port 212-2, which has a fusion point P. This causes the control unit 24 to generate a waveform with constant intensity, as shown in Figure 4(A).
[0039] Further, for example, when the control unit 24 causes the reflection light generation unit 21 to generate a waveform that is ON / OFF modulated as shown in (C) of FIG. 4 as a specific waveform pattern, the control unit 24 controls the position of the prism 215 so that light is input to the output port 212-2 having the fusion point P as shown in FIG. 5 from time t1 to time t2. Next, the control unit 24 controls the position of the prism 215 so that light is input to the output port 212-1 having no fusion point P as shown in FIG. 6 from time t2 to time t3. By repeating this operation at a predetermined time interval (for example, a cycle of 0.1 seconds), the control unit 24 generates a waveform that is ON / OFF modulated as shown in (C) of FIG. 4. In this way, the control unit 24 generates reflected light such that the intensity of the reflected light repeats between large and small at a predetermined time interval.
[0040] In the above description, a configuration for controlling based on the presence or absence of the fusion point P has been shown. However, depending on the output port 212, it is also assumed that all the output ports 212 have the fusion point P. In such a case, the control unit 24 may control the position of the prism 215 based on the number of fusion points P. It is assumed that the output port 212 with the largest number of fusion points P has a large amount of reflected light (high intensity of reflected light), and the output port 212 with the smallest number of fusion points P has a small amount of reflected light (low intensity of reflected light).
[0041] Therefore, for example, when the control unit 24 causes the reflection light generation unit 21 to generate a waveform that is intensity modulated as shown in (B) of FIG. 4 as a specific waveform pattern, the control unit 24 controls the position of the prism 215 so that light is input to the output port 212 with the smallest number of fusion points P from time t1 to time t2. Next, the control unit 24 controls the position of the prism 215 so that light is input to the output port 212 with the largest number of fusion points P from time t2 to time t3. By repeating this operation at a predetermined time interval, the control unit 24 generates a waveform that is intensity modulated as shown in (B) of FIG. 4.
[0042] The intensity of the light transmitted by optical power supply is often set to be much higher than the intensity of general optical communication (for example, the light intensity of FLET'S (registered trademark)) as described above. That is, since the optical power reaching the optical communication device 20 side is strong, the intensity of the reflected light reflected by the optical communication device 20 is also relatively high. Therefore, it can be measured on the optical communication device 10 side without being buried in environmental noise or the like, and thus can be used for vital monitoring.
[0043] (Operation) FIG. 7 is a sequence diagram showing the processing flow of the optical communication system 100 in the first embodiment. It is assumed that a specific waveform pattern and intensity are defined between the optical communication device 10 and the optical communication device 20 at the start of the processing in FIG. 7.
[0044] The light source 11 of the optical communication device 10 sends out light of a specific wavelength (power supply light) used for power supply (step S101). The power supply light sent out from the light source 11 is input to the first port 121 of the circulator 12. The power supply light input to the first port 121 of the circulator 12 is output from the second port 122 of the circulator 12 to the optical fiber F. The power supply light output to the optical fiber F is input to the input port 211 of the reflected light generation unit 21 of the optical communication device 20 (step S102). The power supply light input to the input port 211 of the reflected light generation unit 21 is input to one of the output ports 212 via the switching unit 213. At this time, the switching unit 213 provided in the reflected light generation unit 21 controls the position of the prism 215 so that the power supply light is input to one of the output ports 212 according to the control of the control unit 24.
[0045] The power supply light input to the output port 212 is reflected within the output port 212 and is input to the PD 22 connected to the outside of the output port 212. The PD 22 converts the input light into electric power (step S103). The PD 22 stores the converted electric power in the storage battery 23 (step S104). Also, the reflected light generation unit 21 generates reflected light having a specific waveform pattern and intensity by moving the prism of the switching unit 213 according to the control of the control unit 24 (step S105). The reflected light generated by the reflected light generation unit 21 is output from the input port 211 to the optical fiber F (step S106).
[0046] The reflected light output to the optical fiber F is input to the second port 122 of the circulator 12 of the optical communication device 10. The reflected light input to the second port 122 of the circulator 12 is input to the reflected light measuring unit 13 from the third port 123 (step S107). The reflected light measuring unit 13 measures the intensity of the input reflected light (step S108). The reflected light measuring unit 13 determines the state of the optical fiber F based on the measurement results (step S109). For example, if the waveform pattern and intensity of the reflected light obtained based on the measurement results match a predetermined waveform pattern and intensity, the reflected light measuring unit 13 determines that there is no abnormality in the state of the optical fiber F. On the other hand, if the waveform pattern and intensity of the reflected light obtained based on the measurement results do not match a predetermined waveform pattern and intensity, the reflected light measuring unit 13 determines that there is an abnormality in the state of the optical fiber F.
[0047] In the optical communication system 100 configured as described above, the optical communication device 20 includes a reflected light generation unit 21 that generates reflected light with a specific waveform pattern and intensity using light transmitted from the optical communication device 10 connected via the optical fiber F, and sends the generated reflected light to the optical communication device 10. The optical communication device 10 detects the state of the optical fiber F based on the reflected light with the specific waveform pattern and intensity. With this configuration, the optical communication device 20 does not need to have a light source as in the conventional system, and power consumption can be reduced. Furthermore, the optical communication device 10 detects the state of the optical fiber F using a specific waveform pattern and intensity. The specific waveform pattern and intensity do not depend on the shape of the fiber fracture surface. Therefore, the state of the optical fiber F can be detected with higher accuracy than in the conventional system, without depending on the shape of the fiber fracture surface. As a result, it becomes possible to detect the state of the optical fiber with high accuracy while reducing the power consumption of the optical communication device.
[0048] Furthermore, the optical communication device 20 generates reflected light by directly reflecting a portion of the light transmitted from the optical communication device 10. Specifically, the optical communication device 20 generates reflected light by directly reflecting a portion of the light transmitted from the optical communication device 10 using a mechanical optical switch or a MEMS optical switch, as shown in Figure 5. This configuration allows for the generation of reflected light with a simple setup. As a result, it becomes possible to detect the state of the optical fiber with high precision while keeping the power consumption of the optical communication device low.
[0049] (Second Embodiment) In the second embodiment, a configuration is described in which the light arriving at the optical communication device is input to an optical modulator internally for external modulation, and reflected light is generated using a reflector or the like. However, if all the light arriving at the optical communication device is sent back, optical power supply will not be possible. Therefore, in the second embodiment, the light arriving at the optical communication device is first decoupled according to its wavelength, and a modulated signal is generated using only a portion of the light.
[0050] Figure 8 shows an example configuration of the optical communication system 100a in the second embodiment. The optical communication system 100a comprises one optical communication device 10 and one optical communication device 20a. The optical communication device 10 and the optical communication device 20a are connected by an optical fiber F. The functional configuration of the optical communication device 10 is the same as in the first embodiment. The light source 11 of the optical communication device 10 emits power supply light in a specific wavelength range, as shown in Figure 8. This is because if power supply light is emitted at a certain wavelength, the optical communication device 20a cannot decouple it by wavelength.
[0051] (Configuration of Optical Communication Device 20a) The configuration of the optical communication device 20a will now be described. The optical communication device 20a comprises a reflected light generation unit 21a, a PD 22, a storage battery 23, and an optical demultiplexing unit 25. The optical communication device 20a differs from the optical communication device 20 in that it has a reflected light generation unit 21a instead of the reflected light generation unit 21, does not have a control unit 24, and newly includes an optical demultiplexing unit 25. The other configurations of the optical communication device 20a are the same as those of the optical communication device 20. The following will focus on the differences from the optical communication device 20.
[0052] The optical demultilayer unit 25 demultilayers the light transmitted from the optical communication device 10 according to its wavelength. For wavelength-specific demultilayering, for example, a dielectric multilayer filter is used. The optical demultilayer unit 25 outputs some of the demultilayered wavelengths of the power supply light to the reflected light generation unit 21a and outputs the other wavelengths of the power supply light to the PD 22. It is desirable that the amount of light used for power supply is greater than the amount of light used for generating reflected light in the optical demultilayer unit 25. The amount of energy to be demultilayered and reflected by the optical demultilayer unit 25 should be determined in advance. At a minimum, the amount of demultilayering should be designed so that the reflected light reaches the optical communication device 10 with an intensity equal to or greater than the minimum intensity required for the reflected light measurement unit 13 on the optical communication device 10 side to detect the state of the optical fiber F.
[0053] The reflected light generation unit 21a generates reflected light with a specific waveform pattern using light transmitted from the optical communication device 10. In this case, the reflected light generation unit 21a generates reflected light with a specific waveform pattern using light delimited by the optical demultiplexer 25. The reflected light generation unit 21a consists of an optical modulator 26 and an optical reflector 27. The optical modulator 26 generates a modulated signal by externally modulating the light delimited by the optical demultiplexer 25. As a result, the optical modulator 26 generates a modulated signal with a specific waveform pattern. The optical reflector 27 reflects the modulated signal generated by the optical modulator 26. As a result, the optical reflector 27 generates reflected light with a specific waveform pattern.
[0054] The reflected light generated by the optical reflector 27 is output to the optical fiber F via the optical modulator 26 and the optical demultiplexer 25. Subsequently, the reflected light is input to the reflected light measuring unit 13 via the circulator 12 of the optical communication device 10, as in the first embodiment. The reflected light measuring unit 13 determines the state of the optical fiber F using the same method as in the first embodiment.
[0055] In the optical communication system 100a configured as described above, the optical communication device 20a externally modulates the light transmitted from the optical communication device 10 and generates reflected light by reflecting the externally modulated modulation signal. Thus, although the configuration of the optical communication device 20a in the optical communication system 100a differs from that of the optical communication device 20 in the first embodiment, the point of detecting the state of the optical fiber F using reflected light remains the same. Therefore, the same effects as in the first embodiment can be obtained.
[0056] The optical communication device 20a includes an optical demultiplexer 25 that demultiplexes the light emitted from the optical communication device 10 into light used for power supply and light used for generating reflected light, according to its wavelength. As a result, even if a portion of the light emitted from the optical communication device 10 is used to generate reflected light, the remaining light can be used for power supply. Therefore, the optical communication device 20a can generate reflected light while simultaneously storing energy. Consequently, even when using equipment that cannot receive a stable power supply, it becomes possible to detect the state of the optical fiber with high precision while keeping power consumption low.
[0057] (Third Embodiment) In the first embodiment, the case where there is one power supply target was described as an example. The present invention is also applicable when there are multiple power supply targets (not a single star configuration, but for example, a PON (Passive Optical Network) configuration). Therefore, in the third embodiment, the case where there are multiple power supply targets as in the first embodiment will be described.
[0058] Figure 9 shows an example configuration of the optical communication system 100b in the third embodiment. The optical communication system 100b comprises one optical communication device 10 and N (where N is an integer of 2 or more) optical communication devices 20. The optical communication device 10 and each optical communication device 20 are connected by optical fibers F and optical branching units 40. The optical communication device 10 is, for example, an OLT (Optical Line Terminal), and the optical communication devices 20 are, for example, ONUs (Optical Network Units).
[0059] The optical combining / branching unit 40 branches or combines the input optical signal. The optical combining / branching unit 40 is, for example, an optical coupler. The optical combining / branching unit 40 branches the optical signal sent from the optical communication device 10 and outputs it to each optical communication device 20. The optical combining / branching unit 40 combines the optical signals sent from each optical communication device 20 and outputs it to the optical communication device 10.
[0060] Each optical communication device 20 has the same configuration and performs the same processing as the optical communication device 20 shown in the first embodiment. However, as the specific waveform pattern generated by the reflected light generation unit 21 of each optical communication device 20, a specific waveform pattern generated by, for example, a method of changing the reflection intensity over time (i.e., intensity modulation) may be used. However, the reflected light may be superimposed (mixed) on the optical communication device 10 side, making it difficult to determine which communication partner is operating normally.
[0061] Therefore, as in the third embodiment, in the case of one-to-many connection (when there are multiple devices to be powered), it is desirable that the reflected light generation unit 21 of each optical communication device 20 generates a specific waveform pattern using a modulation method that can be separated even when superimposed (for example, frequency modulation or phase modulation). For example, the reflected light generation unit 21 of optical communication device 20-1 generates a frequency f １ The reflected light is generated, and the reflected light generation unit 21 of the optical communication device 20-N generates reflected light at frequency f Ｎ By designing the optical communication device 10 to generate reflected light, it is possible to determine which optical communication device 20 generated the reflected light that has arrived by observing the frequency of the reflected light.
[0062] As described above, the specific process for generating reflected light of different frequencies in the reflected light generation unit 21 of each optical communication device 20 will be explained using Figure 10. As explained in the first embodiment, the reflected light generation unit 21 of each optical communication device 20 can dynamically switch the path through which the optical signal is transmitted by switching the combination of the input port 211 and the output port 212 in the switching unit 213. Therefore, by changing the frequency of switching by the switching unit 213 for each optical communication device 20 (making it faster or slower), the waveform can be changed as shown in Figure 10(A) and Figure 10(B). This is equivalent to generating reflected light of different frequencies. Therefore, each optical communication device 20 performs frequency modulation (or a process close to it) by performing the above-described process. As a result, the reflected light generation unit 21 of each optical communication device 20 can generate reflected light of different frequencies. Note that the frequency of reflected light to be generated by the reflected light generation unit 21 of each optical communication device 20 can be adjusted between the optical communication device 10 and each optical communication device 20.
[0063] The reflected light measuring unit 13 of the optical communication device 10 measures the input optical signal. The reflected light measuring unit 13 determines that there is no abnormality in the optical fiber F if the waveform obtained as a result of the measurement has a predetermined specific waveform pattern. The reflected light measuring unit 13 determines that there is an abnormality in the optical fiber F if an optical signal is not obtained within a predetermined time from the output of light from the light source 11, or if the waveform obtained as a result of the measurement does not have a predetermined specific waveform pattern. As described above, the reflected light measuring unit 13 can determine which optical communication device 20 generated the reflected light measured by looking at the frequency of the reflected light, and therefore can also identify which optical communication device 20 the optical fiber F connected to has an abnormality.
[0064] For example, if the reflected light measuring unit 13 determines that there is no abnormality in the state of the optical fiber F based on the reflected light sent from the optical communication device 20-1, and determines that there is an abnormality in the state of the optical fiber F based on the reflected light sent from the optical communication device 20-N, it can identify that there is an abnormality in the state of the optical fiber F connecting the optical merging / branching unit 40 and the optical communication device 20-N.
[0065] Furthermore, for example, if the reflected light measuring unit 13 determines that an abnormality has occurred in the state of the optical fiber F based on the reflected light transmitted from all optical communication devices 20, it can identify that an abnormality has occurred in the state of the optical fiber F connecting the optical communication device 10 and the optical merging / branching unit 40.
[0066] According to the optical communication system 100b in the third embodiment configured as described above, even when there are multiple optical communication devices 20 that generate reflected light having a specific waveform pattern, the same effects as in the first embodiment can be obtained.
[0067] (Fourth Embodiment) In the second embodiment, the case where there is one power supply target was described as an example. The present invention is also applicable when there are multiple power supply targets. Therefore, in the fourth embodiment, the case in the second embodiment where there are multiple power supply targets will be described.
[0068] Figure 10 shows an example configuration of an optical communication system 100c in a fourth embodiment. The optical communication system 100c comprises one optical communication device 10 and N optical communication devices 20a. The optical communication device 10 and each optical communication device 20a are connected by an optical fiber F and an optical splitter 40. The optical communication device 10 is, for example, an OLT, and the optical communication devices 20a are, for example, ONUs.
[0069] The optical combining / branching unit 40 branches or combines the input optical signal. The optical combining / branching unit 40 is, for example, an optical coupler. The optical combining / branching unit 40 branches the optical signal sent from the optical communication device 10 and outputs it to each optical communication device 20a. The optical combining / branching unit 40 combines the optical signals sent from each optical communication device 20a and outputs it to the optical communication device 10.
[0070] Each optical communication device 20a performs the same configuration and the same processing as the optical communication device 20a shown in the second embodiment. However, as a specific waveform pattern generated by the reflected light generation unit 21a of each optical communication device 20a, for example, a specific waveform pattern generated by a method of changing the reflection intensity over time (i.e., intensity modulation) may be used. However, the reflected light is superimposed (mixed) on the optical communication device 10 side, and it may be difficult to determine which communication partner is operating normally.
[0071] Therefore, in the case of one-to-many connection (when there are multiple power supply targets) as in the fourth embodiment, it is desirable that the reflected light generation unit 21a of each optical communication device 20a generates a specific waveform pattern using a modulation method (such as frequency modulation or phase modulation) that can be separated even when superimposed. For example, the optical modulator 26 included in the reflected light generation unit 21a of the optical communication device 20a-1 performs frequency modulation at frequency f １ to generate a modulation signal of frequency f １ The optical modulator 26 included in the reflected light generation unit 21a of the optical communication device 20a-N performs frequency modulation at frequency f Ｎ to generate a modulation signal of frequency f Ｎ The optical reflector 27 included in the reflected light generation unit 21a of the optical communication device 20a-1 reflects the modulation signal of frequency f １ to generate reflected light of frequency f １ The optical reflector 27 included in the reflected light generation unit 21a of the optical communication device 20a-N reflects the modulation signal of frequency f Ｎ to generate reflected light of frequency f Ｎ By designing the configuration of the optical communication device 20a in this way, it is possible to determine which optical communication device 20a the reflected light that has arrived was generated by by looking at the frequency of the reflected light in the optical communication device 10.
[0072] For example, when the reflected light measurement unit 13 determines that there is no state abnormality in the optical fiber F based on the reflected light sent from the optical communication device 20a-1, and determines that there is a state abnormality in the optical fiber F based on the reflected light sent from the optical communication device 20a-N, it is possible to specify that there is an abnormality in the state of the optical fiber F connecting between the optical multiplexer / demultiplexer 40 and the optical communication device 20a-N.
[0073] Furthermore, for example, if the reflected light measuring unit 13 determines that an abnormality has occurred in the state of the optical fiber F based on the reflected light transmitted from all optical communication devices 20a, it can identify that an abnormality has occurred in the state of the optical fiber F connecting the optical communication device 10 and the optical merging / branching unit 40.
[0074] According to the optical communication system 100c in the fourth embodiment configured as described above, even if there are multiple optical communication devices 20 that generate reflected light with a specific waveform pattern, the same effects as in the second embodiment can be obtained.
[0075] (Modifications common to the first or third embodiment) The reflected light generation unit 21 shown in the first and third embodiments was described using a mechanical optical switch having 1 input and 2 outputs (one input port 211 and two output ports 212) as an example, but the number of inputs and outputs in the reflected light generation unit 21 is not limited. For example, the mechanical optical switch as the reflected light generation unit 21 may have a configuration that includes three or more output ports, as shown in Figure 11.
[0076] Figure 11 shows another example of the reflected light generation unit 21. As shown in Figure 11, the reflected light generation unit 21 includes an input port 211, four output ports 212-1 to 212-4, and a switching unit 213. By varying the number of fusion points P in the four output ports 212-1 to 212-4, multiple levels of reflection can be represented. For example, as shown in Figure 11, output port 212-1 has 0 fusion points P, output port 212-2 has 1 fusion point P, output port 212-3 has 2 fusion points P, and output port 212-4 has 3 fusion points P. This allows for the representation of four levels of reflection: 0 when using output port 212-1, 1 when using output port 212-2, 2 when using output port 212-3, and 3 when using output port 212-4. By increasing the number of output ports 212 in this way, it is possible to generate any waveform as shown in Figure 12.
[0077] Since any waveform can be generated as shown in Figure 12 by increasing the number of output ports 212, each optical communication device 20 in the third embodiment may be configured to produce a frequency-modulated waveform with even smoother time variation than the waveform shown in Figure 10.
[0078] (Modifications common to the first to fourth embodiments) In the embodiments described above, an optical power supply system that supplies optical power from the optical communication device 10 to the optical communication devices 20 and 20a was described as an example of an optical communication system, and therefore the optical communication devices 20 and 20a were equipped with a configuration for storing the supplied light (for example, a PD 22 and a storage battery 23). In contrast, if the optical communication devices 20 and 20a are devices that are supplied with a stable power supply, the optical communication devices 20 and 20a do not need to be equipped with a configuration for storing the supplied light (for example, a PD 22 and a storage battery 23). In this configuration, the first to fourth embodiments are similarly applicable, and the control unit 24 can perform similar processing on the communication light instead of the supplied light (path switching by the reflected light generation unit 21 and generation of reflected light by demultiplexing). In this configuration, the optical communication device 20a in the second and fourth embodiments does not need to separate the light used for power supply from the light used for generating reflected light. Therefore, the optical communication device 20a in the second and fourth embodiments does not need to include a configuration for storing power supply light (for example, PD 22 and battery 23) and an optical demultiplexing unit 25. In the first to fourth embodiments, the control unit 24 controlled the reflected light using power supply light, but it is also possible to perform similar processing (path switching by the reflected light generation unit 21 or generation of reflected light by demultiplexing) on other light (for example, communication light) instead of reflected light. In the first to fourth embodiments, it is also possible to use the power obtained by PD 22 directly as power without storing it in the battery 23. In that case, the optical communication devices 20 and 20a in each embodiment do not need to include a battery 23.
[0079] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.
[0080] The present invention can be applied to a system in which multiple optical communication devices are connected by optical fibers.
[0081] 10...Optical communication device, 11...Light source, 12...Circulator, 13...Reflected light measuring unit, 20, 20-1 to 20-N, 20a, 20a-1 to 20a-N...Optical communication device, 21, 21a...Reflected light generation unit, 22...PD, 23...Storage battery, 24...Control unit, 25...Optical demultiplexer, 26...Optical modulator, 27...Optical reflector, 211...Input port, 212, 212-1 to 212-2...Output port, 213...Switching unit, 214...Lens, 215...Prism, 100, 100a, 100b, 100c...Optical communication system
Claims
1. An optical communication device comprising: a reflected light generation unit that uses light emitted from an optical communication device to be communicated with, connected via an optical fiber, to generate reflected light having a specific waveform pattern for detecting the state of the optical fiber, and sends the generated reflected light to the optical communication device to be communicated with.
2. The optical communication device according to claim 1, wherein the reflected light generation unit generates the reflected light by directly reflecting a portion of the light transmitted from the optical communication device to be communicated.
3. The optical communication device according to claim 1, wherein the reflected light generation unit externally modulates light transmitted from the optical communication device to be communicated and generates the reflected light by reflecting the externally modulated modulated signal.
4. A method for detecting the state of an optical fiber, comprising: generating reflected light having a specific waveform pattern for detecting the state of the optical fiber using light emitted from an optical communication device to be communicated with via an optical fiber; sending the generated reflected light to the optical communication device to be communicated with; and the optical communication device to be communicated with detecting the state of the optical fiber based on the reflected light.