JP4984775B2 - Optical communication system, optical communication device, and optical repeater - Google Patents

Description

The present invention is an optical communication device constituting the optical communication system and optical communication system, a 及 Beauty optical repeater device, in particular, each of the subscriber-side device installed in a plurality of subscriber premises utilizing an optical communication system optical communication devices constituting the optical communication system and optical communication system to improve the reception sensitivity by the line terminal of the light emitting signal light, relates 及 beauty optical repeater device.

  Conventionally, Internet communication methods include ADSL (Asymmetric Digital Subscriber Line) using a telephone line, CATV (Community Antenna Television) using a coaxial cable, and FTTH (Fiber To The Home) using an optical fiber. In recent years, due to the rapid spread of Internet communication for home use, there are many cases in which subscribers shift from conventional metal communication to optical communication.

As a network configuration for Internet communication, a single star type (hereinafter referred to as SS type) in which a station side device installed in a telephone station and a subscriber side device installed in each subscriber house are connected one-to-one. There is a Double Star type (hereinafter referred to as DS type) in which a station side device and a plurality of subscriber side devices are connected. In the DS type, one cable branches in the route by the number of subscribers. In the DS type, the active double star (hereinafter referred to as ADS) uses an active element in a branching portion, and the passive double star (hereinafter referred to as PDS) uses a branching element in a branching portion.

  In recent years, as a method for realizing FTTH, a Passive Optical Network system (hereinafter referred to as a PON system), which is a PDS type optical communication technology, has been proposed (for example, see Patent Documents 1 and 2).

  In the PON system, the signal light emitted from the station-side device is arranged in the transmission path between the station-side device and the plurality of subscriber-side devices in the downstream direction from the station-side device to the plurality of subscriber-side devices. The light is branched into a plurality of optical fibers by the branch element and received by each of the plurality of subscriber side devices. Further, in the upstream direction from the plurality of subscriber-side devices to the station-side device, the signal lights emitted from the plurality of subscriber-side devices are transmitted through the optical fibers connected to the plurality of subscriber-side devices. Then, the light is received by the station side device via a branch element arranged in the transmission path between the station side device and the plurality of subscriber side devices. In the PON system, even when the number of subscriber-side devices increases, a single optical fiber is used between the station-side device and the subscriber-side device as a signal light transmission path between the station-side device and the branch element. Therefore, there is an advantage that FTTH can be constructed economically compared with the SS type.

  In general, the wavelength of the signal light in each of the downlink and uplink directions is divided using a wavelength multiplexing filter (hereinafter referred to as a WDM filter), and in the downlink direction, time division multiplexing (hereinafter referred to as TDM) is used as the uplink. In the direction, one optical fiber is shared in the downlink direction and the uplink direction using time division multiple access (hereinafter referred to as TDMA). In FTTH, an optical line terminal (hereinafter referred to as OLT) is provided as a station side device. Also, an optical network unit (hereinafter referred to as ONU) is provided as a subscriber side device. The plurality of signal lights in the upstream direction are controlled by the OLT of the station side apparatus so as to reach the station side apparatus only within the allocated time, and do not reach the station side apparatus at the same time.

  As a wavelength band used for optical communication, a wavelength in the 1490 nm band is used as the downstream signal light, and a wavelength in the 1310 nm band is used as the upstream signal light. The configuration of a PON system that has been conventionally used is shown below.

  FIG. 5 is a schematic diagram showing the overall configuration of a conventional typical PON system 50.

  The PON system 50 includes a station side device 51, subscriber side devices 52a, 52b,..., And branch elements 55c, 55c,... Installed between the station side device 51 and the subscriber side devices 52a, 52b,.・ ・ Consists of

  The station side device 51 includes an OLT light emitting / receiving unit 53 including a WDM filter 58 and a branch element 55b. The OLT light emitting / receiving unit 53 includes a light emitting element 55 that emits signal light 60a and a light receiving element 56 that receives signal light 64a, 64b,... Emitted from a plurality of subscriber-side devices 52a, 52b,. Including. The signal light 60a and the signal light 64a, 64b,... Have different wavelengths. The light emitting element 55 and the light receiving element 56 are connected to the WDM filter 58 by optical fibers or optical systems 59a and 59b, respectively. The WDM filter 58 and the branch element 55 b are connected by an optical fiber 59. The other ends of the plurality of optical fibers 61, 61... Branched and connected to the branch element 55b are connected to the branch elements 55c, 55c.

  The plurality of subscriber-side devices 52a, 52b,... Each include a plurality of ONU light emitting / receiving units 54a, 54b,. The plurality of ONU light emitting / receiving units 54a, 54b,... Receive the signal light 60a emitted from the light emitting elements 65a, 65b,. Elements 66a, 66b, ... are provided. The plurality of ONU light emitting / receiving units 54a, 54b,... And the branch elements 55c, 55c, ... are branched and connected by optical fibers 62a, 62b,.

  The WDM filter 58 is made of a dielectric multilayer film and has a function of separating a plurality of signal lights having different wavelengths. By changing the combination of the refractive index and the film thickness of the dielectric multilayer film, the reflection coefficient and the transmission coefficient are given wavelength dependency. In general, it is possible to separate a plurality of signal lights having different desired wavelengths by alternately laminating a material having a high refractive index and a material having a low refractive index.

  The WDM filter 58 includes signal light 60a emitted from the light emitting element 55 of the OLT light emitting / receiving unit 53 and signal light emitted from the plurality of subscriber side devices 52a, 52b... 64a, 64b,... Can be separated by the difference in wavelength, the signal light 60a can be transmitted to the optical fiber 59, and the signal light 64a, 64b.

  In the downstream direction, the signal light 60a emitted from the light emitting element 55 of the OLT light emitting / receiving unit 53 is continuously transmitted by TDM. The signal light 60 a is transmitted through an optical fiber or an optical system 59 a connected to the light emitting element 55. The WDM filter 58 connected to the optical fiber or optical system 59a and the optical fiber or optical system 59b has been emitted from the signal light 60a and the plurality of subscriber side devices 52a, 52b. Are separated by the difference in wavelength, the signal light 60a is transmitted to the optical fiber 59, and the signal light 64a, 64b... Is transmitted to the optical fiber or the optical system 59b. The signal light 60 a is branched into optical fibers 61, 61... By a branch element 55 b connected to the optical fiber 59. The signal lights 61a, 61b,... Transmitted through the optical fibers 61, 61,... Connected to the branch element 55b are the branch elements 55c, 55c,. Branches by the number of subscribers. The signal lights 61a, 61b,... Are transmitted as signal lights 63a, 63b,... Through a plurality of optical fibers 62a, 62b,. Light is received by the light receiving elements 66a, 66b,... Of each of the ONU light receiving / emitting sections 54a, 54b,... Connected to the fibers 62a, 62b,.

  In the upstream direction, the plurality of ONU light emitting / receiving sections 54a, 54b,..., Emitted from the respective light emitting elements 65a, 65b,. .. The branch element 55c is transmitted via the plurality of optical fibers 62a, 62b... Connected to the plurality of optical fibers 62a, 62b. , 55c... Are transmitted through the optical fibers 61, 61. The signal lights 64a, 64b,... Are collected and transmitted to the optical fiber 59 by the branch element 55b connected to the optical fibers 61, 61,. The WDM filter 58 connected to the optical fiber 59 transmits the signal lights 64a, 64b... Transmitted through the optical fiber 59 to the optical fiber or the optical system 59b. The signal light 64a, 64b,... Is received by the light receiving element 56 of the OLT light receiving and emitting unit 53 connected to the optical fiber or the optical system 59b. In the upstream direction, the OLT light emitting / receiving unit 53 of the station side device 51 uses the TDMA to turn on / off the light emitting elements 65a, 65b,. .. Are controlled so that the signal lights 64 a, 64 b... Do not reach the OLT light emitting and emitting unit 53 at the same time.

  In such a conventional optical communication system, the signal light 60a transmitted through one optical fiber is branched and connected by branch elements 55b and 55c, 55c... 61, 61. Are transmitted in accordance with the number of branches of the branch elements 55b and 55c, 55c,..., There is a problem that signal light is lost due to branching. Theoretically, in the downstream and upstream directions, a loss of 3 dB occurs in the case of two distributions, and a loss of 6 dB occurs in the case of four distributions.

In the PON system 50, when an increase in the number of branches due to the number of branching elements 55b and 55c, 55c,... There was a problem that the allowable loss during the period had to be expanded. Specifically, it is conceivable to increase the transmission power of the station side device, improve the reception sensitivity of the subscriber side device, and install an optical amplifier on the optical transmission path. In the downstream direction, the signal light power emitted from the station-side device is high, the wavelength in the 1490/1550 nm band may be used, and the characteristic deterioration is not so much. Moreover, it is easy to install an optical amplifier or the like. However, in the upstream direction, the signal light emitted from the subscriber side device has lower power than the signal light emitted from the station side device, and it is necessary to consider the influence of characteristic deterioration. When a low-power signal light is amplified using an optical amplifier, the signal light is amplified, but noise light (Amplified Spontaneous Emission, hereinafter referred to as ASE) generated other than the signal light is affected. In the case of the downstream direction, since it is usually installed on the station side that is advantageous in terms of cost, the signal light power before amplification is large, and the generation of noise is small.
JP-A-9-191125 Japanese Patent Laid-Open No. 11-83619

  FIG. 6 is a state diagram in which ASE is generated when an optical amplifier is used in the transmission path of signal light emitted from the station side device 51 in the PON system 50.

  FIG. 6A is a diagram illustrating a state in which reception characteristics are good in the uplink direction, and FIG. 6B is a diagram illustrating a state in which ASE is occurring in the uplink direction. 6A and 6B, the horizontal axis indicates the wavelength λ, and the vertical axis indicates the signal intensity. In FIG. 6B, noise light (arrow part in the figure) is generated on both sides of the wavelength of the signal light. If the ASE portion is cut using a narrow band filter having a wavelength width of 1 nm or 0.1 nm, the reception characteristics are improved. However, since the upstream signal lights 64a, 64b,... Are considered to have different wavelengths in the range of 100 nm, a wide band of 100 nm is necessary for each of the signal lights 64a, 64b,. A filter effective for improvement cannot be used. In order to use a narrow-band filter, it is necessary to control the wavelength of emitted light, resulting in an increase in system cost. Therefore, in order to obtain good reception sensitivity by the light receiving element 56 of the station side device 51 of the signal lights 64a, 64b... Emitted from the plurality of subscriber side devices 52a, 52b. There was a problem that had to be considered.

  Further, when an optical amplifier is installed in the vicinity of the plurality of subscriber-side devices 52a, 52b,... In the upstream direction, there is a problem that the system cost increases.

  Further, when an optical amplifier is installed in the vicinity of the branch elements 55c, 55c,... In the transmission path in the upstream direction, there is a problem that a power source is required for the optical transmission path, resulting in an increase in system cost. Therefore, without using an optical amplifier, the development of an optical receiver that improves the reception sensitivity of the signal light 64a, 64b... Transmitted from the plurality of subscriber devices 52a, 52b. Was desired.

The present invention has been made in view of such circumstances, and includes a plurality of second branch elements installed between a station-side apparatus and a plurality of subscriber-side apparatuses and a first branch element of the station-side apparatus. A plurality of integration / separation means are provided in the middle of the transmission paths of the plurality of first light guides to be connected, and the plurality of integration / separation means and the light receiving elements of the station side device are connected by the plurality of third light guides. Thus, the second signal light emitted from the second light emitting element of each of the plurality of subscriber side devices does not pass through the first branch element of the station side device, and the second light receiving element of the station side device. It is an object of the present invention to provide an optical communication system that receives light and a station-side optical communication apparatus that constitutes the system.
Note that integration refers to mixing optical signals with different wavelengths or transmission directions, and separation refers to dividing optical signals with different wavelengths or transmission directions transmitted by a single core light guide into separate light guides. Show. As the integration / separation means, for example, a WDM filter or a circulator can be used.

  In addition, the present invention provides a plurality of signals emitted from the plurality of third light guides by providing a lens or an optical waveguide between the emission portions of the plurality of third light guides and the second light receiving elements. An object is to provide an optical communication system in which light is efficiently received by a second light receiving element.

 Still another object of the present invention is to provide a bi-directional optical communication system with less loss in the same direction by reducing branch elements related to communication in one direction.

An optical communication system according to the present invention includes a station-side apparatus including a first light-emitting element that emits first signal light and a first branch element that branches the first signal light into a plurality of first light guides. A subscriber-side device that is installed in each of a plurality of subscriber homes and includes a second light-emitting element that emits a second signal light and a first light-receiving element that receives the first signal light; and the station-side device And the plurality of subscriber-side devices, connected to the first branch element by the plurality of first light guides, and the plurality of subscriber-side devices by the plurality of second light guides. A plurality of second branch elements connected to each other; and the station side device further includes a second light receiving element that receives the plurality of second signal lights, and the station side device and the plurality of subscriber sides in an optical communication system for performing bidirectional communication between devices, prior Symbol plurality of first light guide body each transmission path during the And a plurality of integrating / separating means connected to the second light receiving element by a plurality of third light guides, wherein the plurality of integrating / separating means comprise the first signal light and the second signal light. Signal light is integrated / separated, the first signal light is sent to the plurality of second branch elements, and the plurality of second signal lights transmitted through the plurality of second branch elements are sent to the plurality of second branch elements. It is characterized by being guided to the third light guide.

The optical communication device of the present invention is a light emitting element that emits first signal light, a branch element that branches the first signal light into a plurality of fourth light guides, light emitted outside the apparatus, An optical communication device including a light receiving element that receives a plurality of second signal lights respectively guided through a light guide, and is connected to a transmission path of each of the plurality of fourth light guides, A plurality of integration / separation means connected to the light receiving element by a plurality of fifth light guides, wherein the plurality of integration / separation means integrates / separates the first signal light and the second signal light. and, a wherein the first signal light sent outside the device, the plurality of second signal light from outside of the device are to guide the plurality of fifth light guide To do.

  In the optical communication system of the present invention, in the downstream direction, light is emitted from the first light emitting element of the station side device configured by the optical communication apparatus of the present invention and transmitted through the light guide connected to the first light emitting element. The first signal light is branched into a plurality of first light guides by the first branch element connected to the light guide. The plurality of integrating / separating means connected in the middle of the transmission paths of the plurality of first light guides are configured to convert the first signal light and the second signal light emitted from the plurality of subscriber-side devices according to the difference in wavelength. The first signal light is transmitted to the plurality of first light guides, and the second signal light in the upward direction is transmitted to the plurality of third light guides. The first signal light is branched by a plurality of second branch elements connected to the plurality of first light guides, and each of the plurality of subscriber side devices connected to each of the plurality of second light guides. Is received by the first light receiving element.

  In the optical communication system of the present invention, in the upstream direction, the second signal light emitted from the second light emitting elements of each of the plurality of subscriber side devices is connected to the plurality of second light emitting elements. The plurality of first light beams transmitted through the second light guide and connected to the plurality of second branch elements via the plurality of second branch elements connected to the plurality of second light guide bodies. Transmitted through the light guide. The plurality of integration / separation means connected in the middle of the transmission paths of the plurality of first light guides are a plurality of integration / separation means without passing the second signal light through the first branch element of the station side device. And transmitting a plurality of third light guides connected to. The second signal light is received by the second light receiving element of the station side device connected to the plurality of third light guides.

The optical communication system of the present invention is characterized in that a lens or an optical waveguide is provided between the emitting portions of the plurality of third light guides and the second light receiving element.
In the optical communication system of the present invention, the plurality of signal lights emitted from the plurality of third light guides are converged by the lens or the optical waveguide, and the converged signal lights are received by the light receiving element.

An optical communication system of the present invention includes a station-side device and a plurality of subscriber-side devices installed in a plurality of subscriber homes, and one branch element from the station-side device is connected to a plurality of light guides. Each of the plurality of light guides is connected to each of a plurality of branch elements, and each of the plurality of branch elements is further branched and connected to a plurality of other light guides. In an optical communication system that performs bidirectional communication by sharing at least the configuration in an optical path in which the subscriber side device is connected directly or indirectly to the tip of a light guide, the plurality of subscriber sides A path related to communication from a device to the station side device is connected to the station side device from the plurality of light guides without passing through the one branch element .

In the optical communication system according to the present invention, at the time of communication from the subscriber-side device to the station-side device, the light-receiving element is transmitted from each of the plurality of light guides without passing through one branch element from the most station-side device. Since a plurality of signal lights emitted from a plurality of light guides are received, the number of branching elements related to communication in the direction in which light is mixed is larger than the number of stages of branching elements related to communication in the direction in which light branches. The number of steps can be reduced.
Since light is integrated / separated by one stage in the light receiving element, in the optical communication system according to the present invention, the direction in which light is integrated / separated is larger than the number of stages of branching elements involved in communication in the direction in which light is branched. The number of branch elements involved in communication is one stage less.

  The light receiving element described above may be a photoelectric conversion element or an optical amplification element.

  In the case of a photoelectric conversion element, an electric signal output can be obtained. In the case of an optical amplifying element, amplified signal light is output, so that it can be used as an optical repeater.

The optical repeater of the present invention is a device for relaying first and second signal lights to be transmitted in opposite directions, and branches the first signal light input from one to a plurality of sixth light guides A plurality of branching elements that are connected to the transmission path of each of the plurality of sixth light guides and that output the first signal light to the other and a plurality of second signal lights from the other respectively. And a light amplifying element optically coupled so as to input the second signal light output from each of the plurality of integration / separation means via the plurality of seventh light guides. characterized that you and output means for outputting a second signal light amplified by the optical amplifier element to said one.

  In the optical repeater of the present invention, the first signal light is output via the branch element and the integrating / separating means. On the other hand, the plurality of second signal lights pass through the integrating / separating means, enter the optical amplifying element, and are amplified and output by the optical amplifying element.

  The optical repeater according to the present invention receives the first signal light and the second signal light amplified by the optical amplifying element as inputs, and provides the first signal light to the branch element and the amplified second signal light. An integrating / separating means for outputting the signal light to the input side of the first signal light is provided.

  In the optical repeater according to the present invention, the first signal light enters the branch element through the integration / separation means. On the other hand, the amplified second signal light is output to the input side of the first signal light through the integration / separation means.

In the present invention, since the loss due to the branching element is reduced in the upstream direction, an optical amplifier that is conventionally required and a filter for removing noise light caused by the optical amplifier may be unnecessary. Conceivable. The plurality of signal lights emitted from the light emitting elements of the plurality of subscriber side devices are efficiently received by the light receiving element of the station side device without passing through the first branch element of the station side device.
Since the number of branch elements is small in one direction or the upstream direction, the loss is less than in the other direction or the downstream direction, and the burden on the device in the one direction or the upstream direction is reduced.

  In the present invention, the plurality of signal lights transmitted through the plurality of light guides are converged by the lens or the optical waveguide, and the converged signal light is efficiently received by the light receiving element.

  In the present invention, the plurality of signal lights emitted from the emission portions of the plurality of light guides are converged by the lens and efficiently received by the light receiving element.

  Further, in the present invention, it is possible to efficiently receive the plurality of signal lights emitted from the emission portions of the plurality of light guides by the aspherical lens efficiently by the light receiving element. is there.

In the present invention, the plurality of signal lights emitted from the emission portions of the plurality of light guides are converged by the optical waveguide and efficiently received by the light receiving element.
In the present invention, the incident light to the light receiving element of the plurality of signal lights exiting the plurality of optical waveguides and the reflected light from the light receiving element do not interfere with each other, and an accurate signal is received.

  In the present invention, a plurality of signal lights can be amplified and relayed out. Further, the signal light in the reverse direction to the signal light can be branched into a plurality and relayed.

  Hereinafter, the configuration of an optical communication system and an optical receiver according to the present invention will be described with reference to the drawings showing embodiments thereof.

  FIG. 1 is a schematic diagram showing a configuration of a PON system 1 according to an embodiment of the present invention.

  The PON system 1 includes a station side device 11, a plurality of subscriber side devices 12a, 12b,..., A branch element 13b disposed between the station side device 11 and the subscriber side devices 12a, 12b,. 13b...

  The station-side device 11 includes an OLT light emitting / receiving unit 13, a branch element 13a, and a plurality of integration / separation units 17a, 17b,... Using a WDM filter. The OLT light emitting / receiving unit 13 receives the light emitting element 15 that emits the signal light 30a and the light receiving element 16 that receives the plurality of signal lights 37a, 37b,... Emitted from the plurality of subscriber side devices 12a, 12b. Including. The light emitting element 15 and the branch element 13 a are connected by an optical fiber 33. The other ends of the plurality of optical fibers 34a, 34b... Branched and connected to the branch element 13a are connected to the plurality of branch elements 13b, 13b. The plurality of branch elements 13b, 13b,... Are connected to the plurality of ONU light receiving / emitting units 14a, 14b,. Has been. The integrating / separating means 17a, 17b,... Are connected in the middle of the transmission paths of the plurality of optical fibers 34a, 34b, and connected to the light receiving element 16 by the plurality of optical fibers 36a, 36b,. Has been.

  The plurality of subscriber-side devices 12a, 12b,... Each include a plurality of ONU light emitting / receiving units 14a, 14b,. The plurality of ONU light emitting / receiving units 14a, 14b,... Emit light emitting elements 29a, 29b,... That emit a plurality of signal lights 37a, 37b, and the plurality of optical fibers 35a, 35b,. Light receiving elements 45a, 45b... That receive the signal lights 32a, 32b.

  The light receiving element 16 connected to the plurality of optical fibers 36a, 36b,... Constitutes an optical receiver 21 shown in FIG.

  In the downstream direction, the signal light 30a emitted from the light emitting element 15 of the OLT light emitting / receiving unit 13 is continuously transmitted by TDM. The signal light 30 a is transmitted through the optical fiber 33 connected to the light emitting element 15, and a plurality of optical fibers 34 a, 34 b... As signal light 31 a, 31 b, etc. by the branch element 13 a connected to the optical fiber 33. Fork. A plurality of integration / separation means 17a, 17b,... Connected in the middle of each of the plurality of optical fibers 34a, 34b,... Are connected to signal lights 31a, 31b,. The upstream signal lights 37a, 37b,... Emitted from 12b,. The signal lights 31a, 31b... Are branched by the number of subscribers by the plurality of branch elements 13b, 13b... Connected to the plurality of optical fibers 34a, 34b. A plurality of optical fibers 35a, 35b, ... connected to 13b ... are transmitted as signal light 32a, 32b ..., and ONU light receiving / emitting parts 14a, 14b ... each light receiving element 45a, 45b, ... • Received light.

  In the upstream direction, the signal light 37a, 37b,... Emitted from the light emitting elements 29a, 29b,. .. Branch elements 13b, 13b connected to the plurality of optical fibers 35a, 35b,... Are transmitted through the plurality of optical fibers 35a, 35b,. Are collected and transmitted to a plurality of optical fibers 34a, 34b. A plurality of integration / separation means 17a, 17b,... Connected in the middle of each transmission path, the plurality of optical fibers 34a, 34b,... Without the signal light 37a, 37b,. , And transmitted to a plurality of connected optical fibers 36a, 36b. The signal light 37a, 37b,... Is received by the light receiving element 16 connected to the plurality of optical fibers 36a, 36b,. In the upstream direction, the OLT light receiving / emitting unit 13 of the station side device 11 is turned on by the TDMA, and the ONU light receiving / emitting units 14a, 14b ... of the plurality of subscriber side devices 12a, 12b,. .. Are controlled so that the signal lights 37 a, 37 b... Do not reach the OLT light receiving and emitting unit 13 at the same time.

  FIG. 2 is a schematic diagram of the optical receiver 21. In the example shown in the figure, four optical fibers are provided. As shown in FIG. 7, the light emitting portions of the optical fibers 36 a, 36 b, 36 c, and 36 d are equally arranged around the central axis of the ferrule 22. The ferrule 22, the lens 23, and the light receiving element 16 are arranged with their optical axes aligned, and the signal light 37a, 37b, 37c, and 37d emitted from the emitting portions of the optical fibers 36a, 36b, 36c, and 36d are received by the lens 23. It converges on the light receiving element 16. The light receiving element 16 is mounted on the substrate 21a, and the optical fibers 36a, 36b, 36c, 36d, the ferrule 22 and the lens 23 are mounted in a housing 19 arranged so as to cover the substrate 21a. A signal received by the light receiving element 16 and subjected to photoelectric conversion is output from a pin 24 penetrating the substrate 21a. The lens 23 is supported by appropriate members.

  In the optical receiver 21 according to the present invention, since the positions of the sub optical fibers are different, it is desirable that the light receiving element 16 efficiently receives light. For example, it is preferable that the light receiving surface 16a of the light receiving element 16 has a multi-face configuration in which the light receiving surfaces 16a are directed in the emission directions of the plurality of optical fibers.

It is also effective to use an aspheric lens as the lens 23.
Since the signal lights 37a, 37b, 37c, and 37d emitted from the emitting portions of the optical fibers 36a, 36b, 36c, and 36d are diffused according to the aperture ratios of the optical fibers 36a, 36b, 36c, and 36d, not all light The signal light emitted from the fiber is not collected on the lens 23. In high-speed communication of several hundred Mbps or more, the capacity of the light receiving element 16 becomes a problem, and the area of the light receiving surface 16a is limited. In addition, a sensitivity that allows even low-power signal light to be received without error is required. In such a case, it is better to use an aspheric lens. An aspherical lens is a lens that is aspherical by changing the curvature between the central part and the peripheral part of the lens. Use of aspherical lens designed so that signal light 37a, 37b, 37c, 37d emitted from the emitting part of all optical fibers 36a, 36b, 36c, 36d enters lens 23 and there is almost no aberration on the path Then, the emitting part, lens, and light receiving surface are arranged. The emitted signal light 37a, 37b, 37c, 37d passes through the aspherical lens and is condensed in the light receiving surface 16a near the focal point. Since the width of the beam is small near the focal point, a part of the beam is not irradiated to the outside of the light receiving surface 16a, and the signal light can be condensed within a narrow light receiving area. Accordingly, it is possible to receive light equivalent to a case where a single optical fiber is converged and received by a light receiving element with a lens.

  FIG. 3 is a schematic diagram showing another embodiment of the optical receiver 20 of the present invention. This optical receiver 20 uses an optical waveguide. A light receiving element 16 is formed inside or on the upper surface of the PLC substrate 20a. A plurality of light receiving elements 16 have one end positioned on the light receiving surface of the light receiving element 16 and the other end positioned on the end face of the substrate farthest from the light receiving element 16. Four (here, four) optical waveguides 38a, 38b, 38c, and 38d are formed.

  The other ends of the optical waveguides 38a, 38b, 38c, and 38d are opposed to the emitting portions of the optical fibers 36a, 36b, 36c, and 36d. The angles of the optical waveguides 38a, 38b, 38c, 38d with respect to the light receiving surface of the light receiving element 16 are such that the light emitted from the optical fibers 36a, 36b, 36c, 36d is reflected by the light receiving surface, and the other optical fibers 36a, 36b, 36c, It is determined not to enter 36d.

In the above-described embodiment, the light receiving element 16 is formed on the PLC substrate 20a. However, the optical waveguides 38a, 38b, 38c, and 38d are formed from one edge to the opposite other edge, and the light receiving element 16 is formed on the optical waveguides 38a, 38b, It may be configured to be positioned at the light emitting portions 38c and 38d.
In addition, it is preferable to increase the light collection efficiency by interposing a lens between the light receiving element and the optical waveguide.

The light receiving element of the optical receiving apparatus of the present invention is not limited to the photoelectric conversion element as described above, but may be constituted by an optical amplifying element that amplifies incident signal light. In this case, the optical receiving device functions as an optical amplifying device.
That is, the signal light from a plurality of light guides or optical waveguides is focused on the active layer of the optical amplifying element with respect to the input end of the semiconductor optical amplifying element, thereby activating the optical amplifying element with a lens by using a single optical fiber It is possible to receive light equivalent to the case where the light is converged on the layer. By interposing an optical repeater configured using such an optical amplifying device, it is possible to extend the transmission distance from the transmitting device to the receiving device.

FIG. 4 shows the configuration of an optical communication system in which the optical repeater 10 using the optical amplifying device 70 as described above is interposed between the station side device 11 and the subscriber side devices 12a, 12b. It is a schematic diagram. The optical repeater 10 receives the signal light output from the OLT light receiving / emitting unit 13 of the station side device 11 and supplies it to a known optical amplifier 71, and also outputs the output light of the optical amplifying device 70 according to the present embodiment to the OLT. An integration / separation means 17 comprising a WDM filter applied to the light emitting unit 13 is provided. The output of the optical amplifier 71 is branched by the branching element 13a, and passes through the integration / separation means 17a, 17b,... Comprising a WDM filter interposed in each of the plurality of optical fibers 34a, 34b,. , 12b ...
Signal light from the subscriber side devices 12a, 12b is input to the optical amplifying device 70 from the integrating / separating means 17a, 17b... Via the plurality of optical fibers 36a, 36b. Here, efficient condensing is performed, amplified, and sent to the station apparatus 11 side.

It is a schematic diagram which shows the structure of the optical communication system containing the optical communication apparatus of this invention. It is a schematic diagram of the optical receiver of this invention. It is a schematic diagram which shows other embodiment of the optical receiver of this invention. It is a schematic diagram which shows the structure of the optical communication system containing the optical repeater of this invention. It is a schematic diagram which shows the whole structure of the conventional optical communication system. It is explanatory drawing which shows the state in which ASE has generate | occur | produced. It is the VII-VII sectional view taken on the line in FIG.

Explanation of symbols

11 Station side equipment 12a, 12b Subscriber side equipment (ONU)
13 OLT light emitting / receiving section 13a, 13b Branch element 14a, 14b ONU light receiving / emitting section 15, 29a, 29b Light emitting element 16, 45a, 45b Light receiving element 17a, 17b Integration / separation means 20, 21 Light receiving device 23 Lens 34a, 34b, 35a, 35b, 36a, 36b Optical fiber (light guide)
38a, 38b, 38c, 38d Optical waveguide

Claims (6)

A station-side apparatus comprising a first light emitting element that emits first signal light and a first branch element that branches the first signal light into a plurality of first light guides;
A subscriber-side apparatus that is installed in each of a plurality of subscriber homes and includes a second light-emitting element that emits a second signal light and a first light-receiving element that receives the first signal light;
Arranged between the station side device and the plurality of subscriber side devices, connected to the first branch element by the plurality of first light guides, and the plurality of subscriptions by the plurality of second light guides. A plurality of second branch elements connected to the person side device,
The station side device
A second light receiving element for receiving the plurality of second signal lights;
In an optical communication system that performs bidirectional communication between the station side device and a plurality of subscriber side devices ,
Before SL is connected to the plurality of first light guides each transmission path in the middle, with a plurality of integration and separation means connected to said second light receiving element by a plurality of third light guide,
The plurality of integration / separation means are:
Integrating and separating the first signal light and the second signal light;
Sending the first signal light to the plurality of second branch elements;
An optical communication system, wherein the second signal light transmitted through the plurality of second branch elements is guided to the plurality of third light guides.   2. The optical communication system according to claim 1, further comprising a lens or an optical waveguide between an emission part of the plurality of third light guides and the second light receiving element. A station-side device and a plurality of subscriber-side devices installed in each of a plurality of subscriber homes, wherein one branch element from the station-side device is connected to the plurality of light guides, and the plurality of light guides Each of the plurality of branch elements is connected to each of the plurality of branch elements, and each of the plurality of branch elements is further branched and connected to a plurality of other light guides. In an optical communication system that performs bidirectional communication by sharing at least the above-described configuration in an optical path to which the subscriber side device is connected to
A path related to communication from the plurality of subscriber side devices to the station side device is connected to the station side device from the plurality of light guides without passing through the one branch element. Optical communication system. A light emitting element that emits the first signal light, a branch element that branches the first signal light into a plurality of fourth light guides, and a light emitted outside the apparatus and guided through the fourth light guide, respectively. An optical communication device including a light receiving element that receives a plurality of second signal lights to be emitted,
A plurality of integration / separation means connected to the light receiving elements by a plurality of fifth light guides, connected in the middle of the transmission paths of the plurality of fourth light guides,
The plurality of integration / separation means are:
Integrating and separating the first signal light and the second signal light;
Sending the first signal light out of the device ;
Optical communication device characterized by said plurality of second signal light from outside of the device are to guide the light guide of the plurality of fifth. In the device for relaying the first and second signal lights to be transmitted in the opposite directions,
A branch element that branches the first signal light input from one side into a plurality of sixth light guides;
A plurality of integrating / separating means connected in the middle of the transmission paths of the plurality of sixth light guides to output the first signal light to the other and to input the plurality of second signal lights from the other respectively When,
A light amplifying element optically coupled to input the second signal light output from each of the plurality of integration / separation means via the plurality of seventh light guides ;
Output means for outputting the second signal light amplified by the optical amplification element to the one side ;
Optical repeater and wherein a call with a. The first signal light and the second signal light amplified by the optical amplifying element are input, the first signal light is supplied to the branch element, and the amplified second signal light is supplied to the first signal light. 6. The optical repeater according to claim 5 , further comprising integration / separation means for outputting to the input side.

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