JP2006129043A - Optical network unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical network unit of optical wavelength multiplex access system of which an optical transmitter (light source) is shared with no use of an optical demultiplexer. <P>SOLUTION: The optical network unit comprises an optical transmitter which transmits up signal light of wide band, an optical receiver which receives down signal light of specified wavelength, a wavelength filter having such characteristics as multiplex-separates wavelength bands of upload signal light and download signal light, and a cyclic wavelength filter which has such characteristics as transmits (or reflects) total of two wavelengths of one wavelength among the upload signal light wavelengths in wide band and one wavelength among a plurality of download signal light wavelengths. The upload signal light of wide band which is transmitted from the optical transmitter enters the cyclic wavelength filter through the wavelength filter, and a specified wavelength is cut out and outputted. The download signal light which is wavelength-multiplexed enters the cyclic wavelength filter to select a specified wavelength, which is inputted in the optical receiver through the wavelength filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical network unit (ONU) used in an optical wavelength division multiplexing access system.

  FIG. 7 shows a configuration example of a conventional optical wavelength division multiplexing access system (Patent Document 1). In the figure, an optical service unit (OSU) 50 and optical network units (ONUs) 60-1 to 60-n of users 1 to n (n is an integer of 2 or more) include an optical fiber transmission line 71 and an optical power splitter (optical 1 to n via a coupler 72).

  The OSU 50 includes a plurality of optical transmitters 51-1 to 51-n and a wavelength multiplexer 52. Each of the optical transmitters 51-1 to 51-n outputs downlink signal lights having different wavelengths. The wavelength multiplexer 52 wavelength-multiplexes the downlink signal light transmitted from each optical transmitter, and sends it to the optical fiber transmission line 71 as wavelength multiplexed signal light. The wavelength multiplexed signal light is n-branched by the optical power splitter 72 and transmitted to each ONU 60. The ONU 60 of the user k includes a wavelength selection filter 61 and an optical receiver 62. The wavelength selection filter 61 selects the downstream signal light having the wavelength assigned to the ONU 60 of the user k from the wavelength multiplexed signal light. The optical receiver 62 performs a receiving process of the wavelength-selected downlink signal light. The other ONUs also receive the downstream signal light having the assigned wavelength.

  Although there is no description regarding upstream signal light in Patent Document 1, if each ONU 60 transmits upstream signal light having a different wavelength, each upstream signal light is wavelength-multiplexed by the optical power splitter 72 and reaches the OSU 50. To do. In the OSU 50, the upstream signal light from each wavelength-multiplexed ONU is wavelength-multiplexed and demultiplexed, and each optical signal is received and processed, thereby enabling bidirectional communication between the OSU and each ONU.

By the way, when a plurality of ONUs use different wavelengths and perform upstream communication with the OSU, a spectrum slicing method is used as a method for sharing the configuration of an optical transmitter (light source) provided in each ONU. is there. Patent Document 2 proposes a method using a broadband light source (broadband source) having a wide wavelength spectrum width as a light source of each ONU. In this method, instead of the optical power splitter 72 of FIG. 7, an optical demultiplexer having a different transmission wavelength is arranged depending on the input (output) port, and broadband upstream signal light transmitted from each ONU is spectrum-sliced by the optical demultiplexer. To do. Then, by associating the transmission wavelength for each port of the optical demultiplexer with each ONU, it is possible to perform upstream communication with the OSU.
Japanese Patent Publication No. 3-44701 JP-A-8-8878

  In order to share the configuration of the optical transmitter (light source) provided in each ONU by the spectrum slicing method, it is necessary to use an optical demultiplexer instead of the optical power splitter 72.

  An object of the present invention is to provide an optical network unit in which an optical transmitter (light source) can have a common configuration without using an optical demultiplexer in an optical wavelength division multiplexing access system.

  In the first invention, an optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n through an optical fiber transmission line, and the downstream signal light from each OSU to each ONU and each ONU In an optical network unit of an optical wavelength division multiplex access system which arranges the wavelength bands of upstream signal light from the OSU to the OSU so as not to overlap and wavelength-division-transmits downstream signal light and upstream signal light allocated to each ONU. An optical transmitter for transmitting upstream signal light, an optical receiver for receiving downstream signal light of a predetermined wavelength, a wavelength filter having a property of demultiplexing each wavelength band of upstream signal light and downstream signal light, and a wideband A periodic wavelength filter having a characteristic of transmitting (or reflecting) a total of two wavelengths of one of the upstream signal light wavelengths and one of the plurality of downstream signal light wavelengths; The optical transmitter and the optical receiver are connected to the periodic wavelength filter via the wavelength filter, and further connected to the optical fiber transmission line via the periodic wavelength filter. The signal light is input to the periodic wavelength filter through the wavelength filter, and a predetermined wavelength is cut out and output, and the wavelength-division multiplexed downstream signal light is input to the periodic wavelength filter to select the predetermined wavelength, and the wavelength In this configuration, the signal is input to the optical receiver through the filter.

  The periodic wavelength filter used in the first invention is a variable wavelength filter that mechanically or electrically changes its transmission (or reflection) wavelength and simultaneously changes two wavelengths. Further, it is a Fabry-Perot type optical filter that controls the resonator length to change its transmission (or reflection) wavelength and simultaneously change two wavelengths.

  According to a second aspect of the present invention, an optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n through an optical fiber transmission line, and downstream signal light having a wavelength assigned to each ONU and In an optical network unit of an optical wavelength multiplexing access system for wavelength-multiplexed transmission of upstream signal light, an optical transmitter for transmitting broadband upstream signal light, an optical receiver for receiving downstream signal light of a predetermined wavelength, and an input / output position A wavelength filter having a characteristic of transmitting (or reflecting) a total of two wavelengths, one of a wide range of upstream signal light wavelengths and one of a plurality of downstream signal light wavelengths; The optical transmitter and the optical receiver are connected to the optical fiber transmission line through the wavelength filter, and the broadband upstream signal light transmitted from the optical transmitter Is input to, and outputs to the optical fiber transmission path by cutting a predetermined wavelength, the downstream signal light wavelength-multiplexed is input to a wavelength filter, is configured to input to the optical receiver by selecting a predetermined wavelength.

  The wavelength filter used in the second invention transmits one wavelength of the broadband upstream signal light wavelength and reflects the other wavelength at the first input / output position, and a plurality of downstream signals at the second input / output position. It has a characteristic of transmitting one of the signal light wavelengths and reflecting the other wavelengths, and inputs a wideband upstream signal light transmitted from the optical transmitter from the first input / output position to obtain a predetermined wavelength. Cut out and output to the optical fiber transmission line, wavelength multiplexed downlink signal light input from the optical fiber transmission line is input from the first input / output position to be reflected, re-input from the second input / output position, and predetermined The wavelength is selected and output.

  The wavelength filter used in the second invention transmits one wavelength of the broadband upstream signal light wavelength and reflects the other wavelength at the first input / output position, and a plurality of downstream signals at the second input / output position. It has a characteristic of transmitting one of the signal light wavelengths and reflecting the other wavelengths, and inputs a wideband upstream signal light transmitted from the optical transmitter from the first input / output position to obtain a predetermined wavelength. Cut out, re-input from second input / output position, reflect and output to optical fiber transmission line, wavelength-division multiplexed downstream signal light input from optical fiber transmission line is input from second input / output position and predetermined The wavelength is selected and output.

  According to a third aspect of the present invention, an optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n via an optical fiber transmission line, and downstream signal light having a wavelength assigned to each ONU and In an optical network unit of an optical wavelength division multiplexing access system for wavelength-multiplexed transmission of upstream signal light, an optical transmitter for transmitting broadband upstream signal light, an optical receiver for receiving downstream signal light of a predetermined wavelength, and upstream signal light The transmission (or reflection) wavelength differs depending on the input / output position and the separation means that separates the downstream signal light and the downstream signal light, and a total of 2 of one wavelength of the broadband upstream signal light wavelength and one of the multiple downstream signal light wavelengths A wavelength filter having a characteristic of transmitting (or reflecting) the wavelength, and the optical transmitter and the optical receiver are connected to the separation means via the wavelength filter, and further the separation means Then, the broadband upstream signal light transmitted from the optical transmitter is input to the wavelength filter, cut out a predetermined wavelength, and is output to the optical fiber transmission line through the separating means. The multiplexed downstream signal light is input to the wavelength filter through the separating means, and a predetermined wavelength is selected and input to the optical receiver.

  The wavelength filter used in the second invention or the third invention is a variable wavelength filter that changes the transmission (or reflection) wavelength mechanically by changing the input / output position to change two wavelengths simultaneously.

  The optical network unit (ONU) of the present invention spectrum-slices broadband upstream signal light, transmits upstream signal light of a predetermined wavelength, and selects downstream signal light of a predetermined wavelength from the wavelength-multiplexed downstream signal light Therefore, the configuration of the ONU corresponding to each user can be shared without using an optical demultiplexer between the ONU and the OSU.

  Further, by sharing the wavelength filter that performs spectrum slicing of the upstream signal light and the wavelength filter that performs wavelength selection of the downstream signal light, the configuration of the ONU can be simplified.

(First embodiment)
FIG. 1 shows a configuration example of an optical wavelength division multiplexing access system including the first embodiment of the optical network unit of the present invention.

  In the figure, an optical service unit (OSU) 50 and optical network units (ONUs) 10-1 to 10-n of users 1 to n (n is an integer of 2 or more) include an optical fiber transmission line 71 and an optical power splitter (optical 1 to n via a coupler 72). Here, the downstream signal light from the OSU to each ONU and the upstream signal light from each ONU to the OSU are separated or adjacent to each other so as not to overlap.

  The ONU 10 of the user k (the same applies to the ONUs of the other users 1 to n) includes an optical transmitter 11, an optical receiver 12, and a wavelength filter (WDM) having a characteristic of demultiplexing each wavelength band of the upstream signal light and downstream signal light. 13) It is composed of a periodic wavelength filter 14 having periodic transmission characteristics. The optical transmitter 11 and the optical receiver 12 are connected to the periodic wavelength filter 14 via the wavelength filter 13 and further connected to the optical fiber transmission line 71 via the periodic wavelength filter 14.

  A broadband light source is used for the optical transmitter 11 of the ONU 10, and upstream signal light having a wide wavelength spectrum width as shown in the figure is transmitted. As the broadband light source, for example, a super luminescent diode (SLD) or an optical amplifier can be used. When an optical amplifier is used, noise light having a wide wavelength spectrum width is modulated with a transmission signal and transmitted.

  The periodic wavelength filter 14 has a characteristic of transmitting (or reflecting) a total of two wavelengths, that is, one of the broadband upstream signal light wavelengths and one of the plurality of downstream signal light wavelengths. That is, the periodic wavelength filter 14 has at least two transmission (or reflection) peaks. Thereby, when the broadband upstream signal light transmitted from the optical transmitter 11 is input to the periodic wavelength filter 14 via the wavelength filter 13, a predetermined wavelength is cut out and output. The upstream signal lights having different wavelengths output from each ONU are wavelength-multiplexed by the optical power splitter 72 and transmitted to the OSU 50. On the other hand, the downlink signal light transmitted from the OSU 50 to each ONU 10 after being wavelength-multiplexed is input to the ONU periodic wavelength filter 14 to select a predetermined wavelength, and is transmitted to the optical receiver 12 via the wavelength filter 13. input. In this way, bidirectional communication between the OSU 50 and each ONU 10 is realized.

  In the present embodiment, the optical transmitter 11 of each ONU 10 is configured to use a broadband light source that transmits broadband upstream signal light, so that the configuration of each ONU can be shared. However, the total two wavelengths of the wavelength extracted from the broadband upstream signal light by the periodic wavelength filter 14 and the wavelengths selected from the plurality of wavelength-multiplexed downstream signal lights are different for each ONU. However, as the periodic wavelength filter 14 that transmits two wavelengths, a variable wavelength filter that changes the transmission (or reflection) wavelength at the same time mechanically or electrically can be used so that the periodic wavelength filter 14 of each ONU can be configured. Can be shared. Thereby, sharing of each ONU is realizable.

  As the periodic wavelength filter 14, for example, when the resonator length is L and the order is m (arbitrary natural number), a Fabry-Perot optical filter that transmits light in the vicinity of a wavelength of 2 L / m can be used. The Fabry-Perot optical filter with L = 155 μm has transmission peaks with wavelengths of 1550 nm and 1565.7 nm corresponding to the orders m = 100 and 99, respectively. An example of the transmission characteristics of the periodic wavelength filter 14 is shown in FIG. The Fabry-Perot type optical filter can change the two transmission peaks at the same time by controlling the resonator length by the piezoelectric effect or the like. With this variable characteristic, it is possible to cope with the case where two different wavelengths are assigned to each ONU.

  Another example of the periodic wavelength filter 14 may be a ring resonator type filter. This ring resonator type filter is disclosed in literature (Giora Griffel, “Vernier Effect in Asymmetrical Ring Resonator Arrays”, IEEE Photonics Technology Letters, Vol. 12, No. 12, pp. 1642-1644, December 2000). Has been.

(Second Embodiment)
FIG. 3 shows an example of the configuration of an optical wavelength division multiplexing access system including the second embodiment of the optical network unit of the present invention.

  In the figure, one optical service unit (OSU) 50 and optical network units (ONUs) 10-1 to 10-n of users 1 to n are connected via an optical fiber transmission line 71 and an optical power splitter (optical coupler) 72. 1: connected to n. Here, it is assumed that the downstream signal light from the OSU to each ONU and the upstream signal light from each ONU to the OSU are alternately arranged with wavelengths corresponding to the downstream and upstream ONUs.

  The ONU 10 of the user k (the same applies to the ONUs of the other users 1 to n) includes an optical transmitter 11, an optical receiver 12, and a gradation filter (wavelength filter) 15 having different transmission (or reflection) wavelengths depending on input / output positions. The The optical transmitter 11 and the optical receiver 12 are connected to the optical fiber transmission line 71 via the gradation filter 15. A broadband light source similar to that of the first embodiment is used for the optical transmitter 11 of each ONU 10.

  An example of the transmission characteristics of the gradation filter 15 is shown in FIG. The gradation filter 15 of the present embodiment has ports 1-1, 1-2, 1-3 at the input / output position 1 and ports 2-1, 2-2 at the input / output position 2. FIG. 4 (1) shows transmission characteristics between the port 1-1 and the port 1-2, and between the port 1-2 and the port 1-3. That is, a predetermined wavelength is transmitted from the port 1-1 to the port 1-2 (or the opposite direction), and other than the predetermined wavelength from the port 1-2 to the port 1-3 (or the opposite direction). Reflects wavelength. FIG. 4 (2) shows input / output characteristics between the port 2-1 and the port 2-2. That is, a predetermined wavelength is transmitted from the port 2-1 to the port 2-2 (or the opposite direction).

  In this embodiment, the optical transmitter 11 and the optical receiver 12 are connected to the ports 1-1 and 2-1 of the gradation filter 15, respectively, the ports 1-3 and 2-2 are connected, and the port 1-2 is connected. It is configured to connect to the optical fiber transmission line 71 as an ONU input / output port. Thus, when the broadband upstream signal light transmitted from the optical transmitter 11 is input to the port 1-1 of the gradation filter 15, a predetermined wavelength is cut out and output from the port 1-2 to the optical fiber transmission line 71. . The upstream signal lights having different wavelengths output from each ONU are wavelength-multiplexed by the optical power splitter 72 and transmitted to the OSU 50. On the other hand, when the downstream signal light transmitted by wavelength multiplexing from the OSU 50 to each ONU 10 is input to the port 1-2 of the ONU gradation filter 15, it is output from the port 1-3 and input to the port 2-2. The predetermined wavelength is cut out and output from the port 2-1 and input to the optical receiver 12. In this way, bidirectional communication between the OSU 50 and each ONU 10 is realized.

  It is known that the gradation filter 15 can realize the above function by forming a dielectric multilayer film on a thin plate-like transparent substrate by vapor deposition. As shown in FIGS. 3 and 4, the transmission (or reflection) wavelength can be changed depending on the input / output position by continuously changing (gradually increasing or decreasing) the film thickness along a certain direction. The film thickness change is discontinuous, and the transmission (or reflection) wavelength may be changed by discretely changing the input / output position.

  In each ONU 10, by adopting a configuration in which either the position of the gradation filter 15 or the position of the means for inputting / outputting light (for example, an optical fiber) is changed, the wavelength interval between the upstream signal light wavelength and the downstream signal light wavelength is changed. The wavelength can be changed while maintaining. In other words, the configuration of the gradation filter 15 of each ONU can be shared, and the sharing of each ONU including the light source of the optical transmitter can be realized.

  In the present embodiment, upstream signal light corresponding to the ONUs 10-1 to 10-n and downstream signal light corresponding to the ONUs 10-1 to 10-n are alternately arranged in the wavelength region as shown in FIG. ing. With such an arrangement, the upstream signal light wavelength and the downstream signal light wavelength in one ONU can be adjacent to each other. If the upstream signal light wavelength and the downstream signal light wavelength are adjacent to each other, the gradation filter 15 can be easily manufactured. If the upstream signal light wavelength and the downstream signal light wavelength are separated, the gradation filter 15 is produced more uniformly over a wide range in order to accurately maintain the wavelength interval between the two wavelengths, but this is not necessarily impossible.

(Third embodiment)
FIG. 5 shows a configuration example of an optical wavelength division multiplexing access system including the third embodiment of the optical network unit of the present invention.

  This embodiment has a configuration in which the port position of the gradation filter 15 in the second embodiment is different. The gradation filter 15 of this embodiment has ports 1-1 and 1-2 at the input / output position 1 and ports 2-1, 2-2 and 2-3 at the input / output position 2. The optical transmitter 11 and the optical receiver 12 are connected to the ports 1-1 and 2-1 of the gradation filter 15, respectively, the port 1-2 and the port 2-3 are connected, and the port 2-2 is an ONU input / output port. It connects to the optical fiber transmission line 71.

  Thus, when the broadband upstream signal light transmitted from the optical transmitter 11 is input to the port 1-1 of the gradation filter 15, a predetermined wavelength is cut out and output from the port 1-2, and further, the port 2-3 And is reflected from the port 2-2 and output to the optical fiber transmission line 71. The upstream signal lights having different wavelengths output from each ONU are wavelength-multiplexed by the optical power splitter 72 and transmitted to the OSU 50. On the other hand, the downstream signal light transmitted by wavelength multiplexing from the OSU 50 to each ONU 10 is input to the port 2-2 of the gradation filter 15 of the ONU, and a predetermined wavelength is cut out and output from the port 2-1. Input to the receiver 12. In this way, bidirectional communication between the OSU 50 and each ONU 10 is realized.

(Fourth embodiment)
FIG. 6 shows a configuration example of an optical wavelength division multiplexing access system including the fourth embodiment of the optical network unit of the present invention.

  In the second embodiment and the third embodiment, this embodiment includes an optical coupler (or WDM filter) 16 that separates upstream signal light and downstream signal light, and uses only the transmission wavelength of the gradation filter 15. It is. The gradation filter 15 of the present embodiment has ports 1-1 and 1-2 at the input / output position 1 and ports 2-1 and 2-2 at the input / output position 2. The optical transmitter 11 and the optical receiver 12 are connected to the ports 1-1 and 2-1 of the gradation filter 15, respectively, and the ports 1-2 and 2-2 are connected to the separation side ports of the optical coupler 16, so that the optical coupler 16 Are connected to the optical fiber transmission line 71 as input / output ports of the ONU.

  Thus, when the broadband upstream signal light transmitted from the optical transmitter 11 is input to the port 1-1 of the gradation filter 15, a predetermined wavelength is cut out and output from the port 1-2. Output to the optical fiber transmission line 71. The upstream signal lights having different wavelengths output from each ONU are wavelength-multiplexed by the optical power splitter 72 and transmitted to the OSU 50. On the other hand, the downstream signal light transmitted from the OSU 50 by wavelength multiplexing to each ONU 10 is input to the port 2-2 of the gradation filter 15 from the optical coupler 16 of the ONU, and a predetermined wavelength is cut out from the port 2-1. Output to the optical receiver 12. In this way, bidirectional communication between the OSU 50 and each ONU 10 is realized.

The figure which shows the structural example of the optical wavelength division multiplexing access system containing 1st Embodiment of the optical network unit of this invention. The figure which shows the example of the transmission characteristic of a periodic wavelength filter. The figure which shows the structural example of the optical wavelength division multiplex access system containing 2nd Embodiment of the optical network unit of this invention. FIG. 6 is a diagram illustrating an example of transmission characteristics of the gradation filter 15. The figure which shows the structural example of the optical wavelength division multiplexing access system containing 3rd Embodiment of the optical network unit of this invention. The figure which shows the structural example of the optical wavelength multiple access system containing 4th Embodiment of the optical network unit of this invention. The figure which shows the structural example of the conventional optical wavelength division multiplexing access system.

Explanation of symbols

10 Optical network unit (ONU)
11 Optical Transmitter 12 Optical Receiver 13 Wavelength Filter (WDM)
14 Periodic wavelength filter 15 Gradation filter 16 Optical coupler 50 Optical service unit (OSU)
51 Optical Transmitter 52 Wavelength Multiplexer 60 Optical Network Unit (ONU)
61 wavelength selection filter 62 optical receiver 71 optical fiber transmission line 72 optical power splitter

Claims (8)

An optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n via an optical fiber transmission line, and downstream signal light from each OSU to each ONU and upstream signals from each ONU to the OSU In an optical network unit of an optical wavelength division multiplex access system that arranges optical wavelength bands so that they do not overlap and wavelength-division-transmits downlink signal light and uplink signal light assigned to each ONU,
An optical transmitter for transmitting broadband upstream signal light, an optical receiver for receiving downstream signal light of a predetermined wavelength, a wavelength filter having a property of demultiplexing each wavelength band of upstream signal light and downstream signal light, A periodic wavelength filter having a characteristic of transmitting (or reflecting) a total of two wavelengths, one of a wideband upstream signal light wavelength and one of a plurality of downstream signal light wavelengths,
The optical transmitter and the optical receiver are connected to the periodic wavelength filter via the wavelength filter, further connected to the optical fiber transmission line via the periodic wavelength filter, and transmitted from the optical transmitter. The wideband upstream signal light is input to the periodic wavelength filter through the wavelength filter, cuts out and outputs a predetermined wavelength, and the wavelength-multiplexed downstream signal light is input to the periodic wavelength filter. An optical network unit, wherein a predetermined wavelength is selected and input to the optical receiver via the wavelength filter. The optical network unit according to claim 1,
The optical network unit, wherein the periodic wavelength filter is a variable wavelength filter that mechanically or electrically changes its transmission (or reflection) wavelength and simultaneously changes the two wavelengths. The optical network unit according to claim 1,
2. The optical network unit according to claim 1, wherein the periodic wavelength filter is a Fabry-Perot type optical filter that changes the transmission (or reflection) wavelength by controlling a resonator length and simultaneously changes the two wavelengths. An optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n through an optical fiber transmission line, and wavelength division multiplexing of downstream signal light and upstream signal light having a wavelength assigned to each ONU is performed. In the optical network unit of the optical wavelength division multiplexing access system for transmission,
An optical transmitter that transmits broadband upstream signal light, an optical receiver that receives downstream signal light of a predetermined wavelength, and the transmission (or reflection) wavelength differs depending on the input / output position. A wavelength filter having a characteristic of transmitting (or reflecting) a total of two wavelengths of one wavelength and one of a plurality of downstream signal light wavelengths;
The optical transmitter and the optical receiver are connected to the optical fiber transmission line via the wavelength filter, and the broadband upstream signal light transmitted from the optical transmitter is input to the wavelength filter, and has a predetermined wavelength. The wavelength-multiplexed downlink signal light is input to the wavelength filter, a predetermined wavelength is selected and input to the optical receiver, and the optical signal is output to the optical fiber transmission line. Optical network unit to be used. The optical network unit according to claim 4,
The wavelength filter transmits one wavelength of the broadband upstream signal light wavelength and reflects the other wavelength at the first input / output position, and the plurality of downstream signal light wavelengths at the second input / output position. And transmitting the other wavelength, and the broadband upstream signal light transmitted from the optical transmitter is input from the first input / output position to cut out a predetermined wavelength. The wavelength-multiplexed downstream signal light that is output to the optical fiber transmission line and input from the optical fiber transmission line is input from the first input / output position to be reflected, and is re-transmitted from the second input / output position. An optical network unit characterized by being configured to input and select and output a predetermined wavelength. The optical network unit according to claim 4,
The wavelength filter transmits one wavelength of the broadband upstream signal light wavelength and reflects the other wavelength at the first input / output position, and the plurality of downstream signal light wavelengths at the second input / output position. And transmitting the other wavelength, and the broadband upstream signal light transmitted from the optical transmitter is input from the first input / output position to cut out a predetermined wavelength. Then, the signal is re-input from the second input / output position, reflected and output to the optical fiber transmission line, and the wavelength-division multiplexed downstream signal light input from the optical fiber transmission line is input from the second input / output position. An optical network unit characterized in that a predetermined wavelength is selected and output. An optical service unit (OSU) and a plurality of n optical network units (ONUs) are connected 1: n through an optical fiber transmission line, and wavelength division multiplexing of downstream signal light and upstream signal light having a wavelength assigned to each ONU is performed. In the optical network unit of the optical wavelength division multiplexing access system for transmission,
Optical transmitter for transmitting broadband upstream signal light, optical receiver for receiving downstream signal light of a predetermined wavelength, separation means for separating upstream signal light and downstream signal light, and transmission (or reflection) depending on input / output positions And a wavelength filter having a characteristic of transmitting (or reflecting) a total of two wavelengths of one wavelength out of a wide range of upstream signal light wavelengths and one of a plurality of downstream signal light wavelengths,
The optical transmitter and the optical receiver are connected to the separation means via the wavelength filter, and further connected to the optical fiber transmission line via the separation means, and transmitted from the optical transmitter in a wide band. Light is input to the wavelength filter, and a predetermined wavelength is cut out and output to the optical fiber transmission line through the separation unit, and the wavelength-multiplexed downstream signal light is input to the wavelength filter through the separation unit. An optical network unit characterized by being configured to input, select a predetermined wavelength, and input to the optical receiver. The optical network unit according to claim 4 or 7,
The optical network unit, wherein the wavelength filter is a variable wavelength filter that mechanically changes an input / output position to change a transmission (or reflection) wavelength thereof to simultaneously change the two wavelengths.

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