Patent Publication Number: US-2022224421-A1

Title: Powered device and power over fiber system

Description:
TECHNICAL FIELD 
     The present disclosure relates to a powered device and a power over fiber system. 
     BACKGROUND ART 
     Recently, there has been studied an optical power supply system that converts electric power into light (called feed light), transmits the feed light, converts the feed light into electric energy, and uses the electric energy as electric power. There is disclosed in Patent Literature 1 an optical communication device that includes: an optical transmitter that transmits signal light modulated with an electric signal and feed light for supplying electric power; an optical fiber including a core that transmits the signal light, a first cladding that is formed around the core, has a refractive index lower than that of the core, and transmits the feed light, and a second cladding that is formed around the first cladding, and has a refractive index lower than that of the first cladding; and an optical receiver that operates with electric power obtained by converting the feed light transmitted through the first cladding of the optical fiber, and converts the signal light transmitted through the core of the optical fiber into the electric signal. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2010-135989 A 
       
    
     SUMMARY OF INVENTION 
     Problem to Solve 
     In optical power supply, a photoelectric conversion element generates heat due to loss in conversion into electric power. Further, in optical power supply, it is difficult to increase or decrease intensity of feed light according to increase or decrease of load. If excess feed light is input, it is converted into heat by the photoelectric conversion element, which results in energy loss. 
     Solution to Problem 
     A powered device of the present disclosure includes: 
     a photoelectric conversion element that receives and converts feed light into electric power; 
     a thermoelectric conversion element disposed such that heat can be conducted thereto from the photoelectric conversion element; and 
     a first power line that transmits, to a load, electric power obtained by conversion by the thermoelectric conversion element. 
     A power over fiber system of the present disclosure includes: 
     a power sourcing equipment that transmits feed light through an optical fiber; and 
     the above powered device that receives the feed light through the optical fiber. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a power over fiber system according to a first embodiment of the present disclosure. 
         FIG. 2  is a block diagram of a power over fiber system according to a second embodiment of the present disclosure. 
         FIG. 3  is a block diagram of the power over fiber system according to the second embodiment of the present disclosure and shows optical connectors and so forth. 
         FIG. 4  is a block diagram of a power over fiber system according to another embodiment of the present disclosure. 
         FIG. 5  is a block diagram of a powered device according to a third embodiment of the present disclosure. 
         FIG. 6  is a block diagram of a powered device according to a fourth embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 
     (1) Outline of System 
     First Embodiment 
     As shown in  FIG. 1 , a power over fiber (PoF) system  1 A of this embodiment includes a power sourcing equipment (PSE)  110 , an optical fiber cable  200 A and a powered device (PD)  310 . 
     In the present disclosure, a power sourcing equipment converts electric power into optical energy and supplies (sources) the optical energy, and a powered device receives (draws) the supplied optical energy and converts the optical energy into electric power. 
     The power sourcing equipment  110  includes a semiconductor laser  111  for power supply. 
     The optical fiber cable  200 A includes an optical fiber  250 A that forms a transmission path of feed light. 
     The powered device  310  includes a photoelectric conversion element  311 . 
     The power sourcing equipment  110  is connected to a power source, and electrically drives the semiconductor laser  111  and so forth. 
     The semiconductor laser  111  oscillates with the electric power from the power source, thereby outputting feed light  112 . 
     The optical fiber cable  200 A has one end  201 A connectable to the power sourcing equipment  110  and the other end  202 A connectable to the powered device  310  to transmit the feed light  112 . 
     The feed light  112  from the power sourcing equipment  110  is input to the one end  201 A of the optical fiber cable  200 A, propagates through the optical fiber  250 A, and is output from the other end  202 A of the optical fiber cable  200 A to the powered device  310 . 
     The photoelectric conversion element  311  converts the feed light  112  transmitted through the optical fiber cable  200 A into electric power. The electric power obtained by the conversion of the feed light  112  by the photoelectric conversion element  311  is driving power needed in the powered device  310 . The powered device  310  is capable of outputting, for an external device(s), the electric power obtained by the conversion of the feed light  112  by the photoelectric conversion element  311 . 
     Semiconductor materials of semiconductor regions of the semiconductor laser  111  and the photoelectric conversion element  311  are semiconductors having a laser wavelength being a short wavelength of 500 nm or less. The semiconductor regions exhibit light-electricity conversion effect. 
     Semiconductors having a laser wavelength being a short wavelength have a large band gap and a high photoelectric conversion efficiency, and hence improve photoelectric conversion efficiency at the power supplying side and the power receiving side in optical power supply, and improve optical power supply efficiency. 
     Hence, as the semiconductor materials, laser media having a laser wavelength (base wave) of 200 nm to 500 nm may be used. Examples thereof include diamond, gallium oxide, aluminum nitride and gallium nitride. 
     Further, as the semiconductor materials, semiconductors having a band gap of 2.4 eV or greater are used. 
     For example, laser media having a band gap of 2.4 eV to 6.2 eV may be used. Examples thereof include diamond, gallium oxide, aluminum nitride and gallium nitride. 
     Laser light having a longer wavelength tends to have a higher transmission efficiency, whereas laser light having a shorter wavelength tends to have a higher photoelectric conversion efficiency. Hence, when laser light is transmitted for a long distance, laser media having a laser wavelength (base wave) of greater than 500 nm may be used as the semiconductor materials, whereas when the photoelectric conversion efficiency is given priority, laser media having a laser wavelength (base wave) of less than 200 nm may be used as the semiconductor materials. 
     Any of these semiconductor materials may be used in one of the semiconductor laser  111  and the photoelectric conversion element  311 . This improves the photoelectric conversion efficiency at either the power supplying side or the power receiving side, and improves the optical power supply efficiency. 
     Second Embodiment 
     As shown in  FIG. 2 , a power over fiber (PoF) system  1  of this embodiment includes a power supply system through an optical fiber and an optical communication system therethrough, and includes: a first data communication device  100  including a power sourcing equipment (PSE)  110 ; an optical fiber cable  200 ; and a second data communication device  300  including a powered device (PD)  310 . 
     The power sourcing equipment  110  includes a semiconductor laser  111  for power supply. The first data communication device  100  includes, in addition to the power sourcing equipment  110 , a transmitter  120  and a receiver  130  for data communication. The first data communication device  100  corresponds to a data terminal equipment (DTE), a repeater or the like. The transmitter  120  includes a semiconductor laser  121  for signals and a modulator  122 . The receiver  130  includes a photodiode  131  for signals. 
     The optical fiber cable  200  includes an optical fiber  250  including: a core  210  that forms a transmission path of signal light; and a cladding  220  that is arranged so as to surround the core  210  and forms a transmission path of feed light. 
     The powered device  310  includes a photoelectric conversion element  311 . The second data communication device  300  includes, in addition to the powered device  310 , a transmitter  320 , a receiver  330  and a data processing unit  340 . The second data communication device  300  corresponds to a power end station or the like. The transmitter  320  includes a semiconductor laser  321  for signals and a modulator  322 . The receiver  330  includes a photodiode  331  for signals. The data processing unit  340  processes received signals. The second data communication device  300  is a node in a communication network. The second data communication device  300  may be a node that communicates with another node. 
     The first data communication device  100  is connected to a power source, and electrically drives the semiconductor laser  111 , the semiconductor laser  121 , the modulator  122 , the photodiode  131  and so forth. The first data communication device  100  is a node in a communication network. The first data communication device  100  may be a node that communicates with another node. 
     The semiconductor laser  111  oscillates with the electric power from the power source, thereby outputting feed light  112 . 
     The photoelectric conversion element  311  converts the feed light  112  transmitted through the optical fiber cable  200  into electric power. The electric power obtained by the conversion of the feed light  112  by the photoelectric conversion element  311  is driving power needed in the second data communication device  300 , for example, driving power for the transmitter  320 , the receiver  330  and the data processing unit  340 . The second data communication device  300  may be capable of outputting, for an external device(s), the electric power obtained by the conversion of the feed light  112  by the photoelectric conversion element  311 . 
     The modulator  122  of the transmitter  120  modulates laser light  123  output by the semiconductor laser  121  to signal light  125  on the basis of transmission data  124 , and outputs the signal light  125 . 
     The photodiode  331  of the receiver  330  demodulates the signal light  125  transmitted through the optical fiber cable  200  to an electric signal, and outputs the electric signal to the data processing unit  340 . The data processing unit  340  transmits data of the electric signal to a node, and also receives data from the node and outputs the data to the modulator  322  as transmission data  324 . 
     The modulator  322  of the transmitter  320  modulates laser light  323  output by the semiconductor laser  321  to signal light  325  on the basis of the transmission data  324 , and outputs the signal light  325 . 
     The photodiode  131  of the receiver  130  demodulates the signal light  325  transmitted through the optical fiber cable  200  to an electric signal, and outputs the electric signal. Data of the electric signal is transmitted to a node, whereas data from the node is the transmission data  124 . 
     The feed light  112  and the signal light  125  from the first data communication device  100  are input to one end  201  of the optical fiber cable  200 , propagate through the cladding  220  and the core  210 , respectively, and are output from the other end  202  of the optical fiber cable  200  to the second data communication device  300 . 
     The signal light  325  from the second data communication device  300  is input to the other end  202  of the optical fiber cable  200 , propagates through the core  210 , and is output from the one end  201  of the optical fiber cable  200  to the first data communication device  100 . 
     As shown in  FIG. 3 , the first data communication device  100  includes a light input/output part  140  and an optical connector  141  attached to the light input/output part  140 , and the second data communication device  300  includes a light input/output part  350  and an optical connector  351  attached to the light input/output part  350 . An optical connector  230  provided at the one end  201  of the optical fiber cable  200  is connected to the optical connector  141 , and an optical connector  240  provided at the other end  202  of the optical fiber cable  200  is connected to the optical connector  351 . The light input/output part  140  guides the feed light  112  to the cladding  220 , guides the signal light  125  to the core  210 , and guides the signal light  325  to the receiver  130 . The light input/output part  350  guides the feed light  112  to the powered device  310 , guides the signal light  125  to the receiver  330 , and guides the signal light  325  to the core  210 . 
     As described above, the optical fiber cable  200  has the one end  201  connectable to the first data communication device  100  and the other end  202  connectable to the second data communication device  300  to transmit the feed light  112 . In this embodiment, the optical fiber cable  200  transmits the signal light  125 ,  325  bidirectionally. 
     As the semiconductor materials of the semiconductor regions, which exhibit the light-electricity conversion effect, of the semiconductor laser  111  and the photoelectric conversion element  311 , any of those described in the first embodiment can be used, thereby achieving a high optical power supply efficiency. 
     Like an optical fiber cable  200 B of a power over fiber system  1 B shown in  FIG. 4 , an optical fiber  260  that transmits signal light and an optical fiber  270  that transmits feed light may be provided separately. Further, the optical fiber cable  200 B may be composed of a plurality of optical fiber cables. 
     (2) Loss Reducing Means of Powered Device 
     Next, a loss reducing means of a powered device will be described. 
     Third Embodiment 
       FIG. 5  is a block diagram of a powered device of a third embodiment to which a loss reducing means is applied. In  FIG. 5 , the components same as those described above are denoted by the same reference signs, and detailed descriptions thereof are omitted. 
     A powered device  310 C of the third embodiment includes a photoelectric conversion element  311  that receives and converts the feed light  112  into electric power, a thermoelectric conversion element  314  disposed such that heat can be conducted thereto from the photoelectric conversion element  311 , a second power line  312  that transmits electric power from the photoelectric conversion element  311  to a load  390 , a first power line  315  that transmits electric power from the thermoelectric conversion element  314  to the load  390 , and a current backflow prevention circuit  319  disposed on the power lines  312 ,  315 . At the light receiving side of the photoelectric conversion element  311 , a lens  313  may be disposed. 
     The load  390  may be, for example, the data processing unit  340 , another/other functional module(s), an external device(s), or any one or more of these. 
     The current backflow prevention circuit  319  includes, for example, backflow prevention diodes D 1 , D 2  disposed on the respective power lines  312 ,  315  to prevent current from flowing from the photoelectric conversion element  311  to the thermoelectric conversion element  314  and vice versa. 
     Due to, for example, Seebeck effect, the thermoelectric conversion element  314  receives heat of the photoelectric conversion element  311  with one side thereof and generates a voltage. When the amount of heat generation of the photoelectric conversion element  311  increases and the thermal gradient of the thermoelectric conversion element  314  is equal to or greater than a certain value, the output voltage of the thermoelectric conversion element  314  increases. When the output voltage of the thermoelectric conversion element  314  exceeds a predetermined voltage, current flows through the backflow prevention diode D 2 , so that electric power is output from the thermoelectric conversion element  314  to the load  390 . A voltage boost circuit that generates a high voltage from a low output voltage of the thermoelectric conversion element  314  and sends the high voltage to the load  390  may be disposed on the first power line  315 . 
     As described above, according to the powered device  310 C of the third embodiment, the heat that the photoelectric conversion element  311  generates by receiving the feed light  112  is converted into electric power by the thermoelectric conversion element  314 , and the electric power is supplied to the load  390 . This can reduce energy loss of the powered device  310 C. 
     There may be a case where the load or the light amount of the feed light  112  fluctuates, and an excess or a deficiency is generated in the feed light  112 . In such a case, due to conversion into electric power that is performed by the thermoelectric conversion element  314 , heat generated from excess feed light  112  is converted, at a later time, into electric power by the thermoelectric conversion element  314 . The electric power obtained by this conversion can be supplied to the load  390  at the timing when a deficiency is generated in the feed light  112 . Thus, according to the powered device  310 C of the third embodiment, an effect of equalizing an excess of the feed light  112  with a deficiency of the feed light  112  can be obtained. 
     The powered device  310 C of the third embodiment is applicable to any of the power over fiber systems  1 A,  1 ,  1 B respectively shown in  FIG. 1 ,  FIG. 2  and  FIG. 4  by replacing the powered device  310  shown in  FIG. 1 ,  FIG. 2  or  FIG. 4 . 
     Fourth Embodiment 
       FIG. 6  is a block diagram of a powered device according to a fourth embodiment to which a loss reducing means is applied. In  FIG. 6 , the components same as those described above are denoted by the same reference signs, and detailed descriptions thereof are omitted. 
     A powered device  310 D of the fourth embodiment includes, in addition to the components of the third embodiment, an abnormality handling part  317  that handles abnormalities when they occur. The abnormalities includes the photoelectric conversion element  311  becoming hot (high temperature). The abnormality handling part  317  is part of load. In the fourth embodiment, the first power line  315  is connected to the abnormality handling part  317 , so that electric power is transmitted from the thermoelectric conversion element  314  to the abnormality handling part  317 . 
     The abnormality handling part  317  is, for example, a cooling fan and cools the photoelectric conversion element  311  generating heat abnormally and components therearound. Alternatively, the abnormality handling part  317  may be a communication device that, for example, outputs a request signal to the power sourcing equipment  110  on the basis of abnormal heat generation of the photoelectric conversion element  311  to request the power sourcing equipment  110  to stop outputting the feed light  112 . The communication device may be configured to output the signal via a metallic line, radio or an optical fiber. Still alternatively, the abnormality handling part  317  may be an imaging device that, when a light receiver of the powered device  310 D generates heat abnormally, outputs the heat generating portion as an image signal. 
     According to this configuration, if the photoelectric conversion element  311  generates heat abnormally, by making use of this heat, a process to handle the abnormality can be performed. For example, the heat generating portion is cooled by a cooling fan, output of the feed light  112  is stopped, or the heat generating portion is output as an image. 
     There may be a case where the photoelectric conversion element  311  goes wrong, but the feed light  112  keeps being input thereto. In this case, while electric power supply from the photoelectric conversion element  311  decreases or stops due to the breakdown, the feed light  112  keeps being input thereto, so that the photoelectric conversion element  311  generates heat abnormally. In such a case, if the abnormality handling part  317  is driven with electric power output from the photoelectric conversion element  311  only, the abnormality handling part  317  may not be driven normally due to the decrease in the electric power. However, in the powered device  310 D of the fourth embodiment, the abnormality handing part  317  is driven with electric power from the thermoelectric conversion element  314 , and hence, even in such a case, can handle abnormalities. 
     In the powered device  310 D of the fourth embodiment, the first power line  315  of the thermoelectric conversion element  314  is connected to the abnormality handling part  317  without merging with the second power line  312  of the photoelectric conversion element  311 . However, in the fourth embodiment, as in the powered device  310 C of the third embodiment, it is possible that the power lines  312 ,  315  merge with one another, and electric power is supplied to the abnormality handling part  317  through the merged power line. 
     The powered device  310 D of the fourth embodiment is applicable to any of the power over fiber systems  1 A,  1 ,  1 B respectively shown in  FIG. 1 ,  FIG. 2  and  FIG. 4  by replacing the powered device  310  shown in  FIG. 1 ,  FIG. 2  or  FIG. 4 . 
     Although some embodiments of the present disclosure have been described above, these embodiments are made for purposes of illustration and example only. The present invention can be carried out in various other forms, and each component may be omitted, replaced or modified/changed within a range not departing from the scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is applicable to a powered device and a power over fiber system. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 A Power over Fiber System 
               1  Power over Fiber System 
               1 B Power over Fiber System 
               100  First Data Communication Device 
               110  Power Sourcing Equipment 
               111  Semiconductor Laser for Power Supply 
               112  Feed Light 
               120  Transmitter 
               125  Signal Light 
               130  Receiver 
               140  Light Input/Output Part 
               141  Optical Connector 
               200 A Optical Fiber Cable 
               200  Optical Fiber Cable 
               200 B Optical Fiber Cable 
               210  Core 
               220  Cladding 
               250 A Optical Fiber 
               250  Optical Fiber 
               260  Optical Fiber 
               270  Optical Fiber 
               300  Second Data Communication Device 
               310  Powered Device 
               310 C Powered Device 
               310 D Powered Device 
               311  Photoelectric Conversion Element 
               312  Second Power Line 
               314  Thermoelectric Conversion Element 
               315  First Power Line 
               317  Abnormality Handling Part 
               319  Current Backflow Prevention Circuit 
             D 1 , D 2  Backflow Prevention Diode 
               320  Transmitter 
               325  Signal Light 
               330  Receiver 
               350  Light Input/Output Part 
               351  Optical Connector 
               390  Load