Optical network system having multiplexer / demultiplexer and optical distributor

Abstract

An external resonator-type laser having a narrow line width according to the present invention includes a gain chip having a laser gain, a lens for collimating light emitted from the gain chip into parallel light, and a wavelength-selective filter for transmitting light having a specific wavelength among the light collimated through the lens, wherein the external resonator-type laser includes both-side heat transfer members that are arranged on both side surfaces of at least one of the lens or the wavelength-selective filter and made of a material having a higher heat transfer rate than the lens and the wavelength-selective filter.

Description

Optical network system having multiplexers / demultiplexers and optical splitters

[0001] The present invention relates to an optical network device having a multiplexer / demultiplexer and an optical splitter.

[0002] Currently, a standard called NG-PON2 (Next Generation - Passive Optical Network version 2) is being agreed upon globally, and this NG-PON2 standard sets four wavelength channels with a signal speed of 10 Gbps for downlink optical signals from the telephone exchange to the subscriber. The wavelength spacing of these four channels is set at 100 GHz or 200 GHz.

[0003] Under the NG-PON2 standard, a subscriber must select a single wavelength for optical reception. This separation of wavelengths is achieved by inputting a channel optical signal of a specific wavelength into an optical receiver using a fixed device that separates wavelengths, thereby enabling the reception of a downlink optical signal. However, optical receivers that separate fixed wavelengths into specific optical fibers and receive optical signals regardless of the type of wavelength coupled to those fibers have faced difficulties in managing optical lines because optical line allocation is not dynamic.

[0004] It can be seen that using 8 channels of wavelengths allows for the provision of more diverse services compared to 4 channels. Compared to existing NG-PON2, which can achieve different types of communication using 4 different wavelengths, increasing the number of channels for wavelength-tunable communication from 4 to 8 channels brings significant economic benefits in that it allows for the provision of more diverse services.

[0005] However, when increasing the number of channels, various problems may arise because a large number of channels must be transmitted or received at once during the transmission or reception process. For example, if the wavelength spacing of 4 channels according to the NG-PON2 standard is 100 GHz and the wavelength tunable filter (e.g., etalon filter) has a change in transmission wavelength according to temperature of 10 GHz / °C, then the wavelength spacing between the first channel and the fourth channel is 300 GHz, and to tune the receiving channel, the temperature of the wavelength tunable filter must be changed by at least 30°C. If this standard is applied to 8 channels, the wavelength spacing between the first channel and the eighth channel is 700 GHz, and to receive the receiving channel, the temperature of the wavelength tunable filter must be changed by at least 70°C. In cases of such large temperature fluctuations, problems arise, including the difficulty in implementing filters capable of withstanding such large temperature changes, the impairment of the durability of various internal components of the optical receiver due to wide temperature ranges, potential airtightness issues resulting from reduced long-term reliability of materials like epoxy used in assembly, and the requirement for high power consumption due to the large temperature variations.

[0006] There is a need to develop technology to solve these problems.

[0007] This application is the result of the following national research and development project.

[0008] [National R&D projects that supported this invention]

[0009] [Project ID] 2420021414

[0010] [Project No.] RS-2023-00281122

[0011] [Ministry Name] Ministry of SMEs and Startups

[0012] [Name of Project Management (Specialized) Agency] Korea Technology Information Promotion Agency for SMEs

[0013] [Research Project Name] SME Technology Innovation Development (Export-Oriented)

[0014] [Research Project Title] Development of NG-PON2 PON-stick Transceiver

[0015] [Name of Project Performing Organization] Fovel Co., Ltd.

[0016] [Research Period] July 17, 2023 – July 16, 2027

[0017] The present invention is proposed to solve the problems of the prior art, and the objective of the present invention is to provide an optical network system having a multiplexer / demultiplexer and an optical distributor that allows the same device to be used for the optical receiver included in the Optical Network Unit (ONU) even when multiple channels are used, by using a multiplexer / demultiplexer to separate multiple channels received at an Optical Line Terminal (OLT) into multiple groups and receiving them at the optical receiver, in accordance with an optical receiver capable of receiving a channel limited to one cycle.

[0018] An optical network system having multiplexers / demultiplexers and optical splitters for solving the above-mentioned problem may include: an OLT-side optical transmitter that transmits N optical channels having different wavelengths to the ONU side; a first multiplexer / demultiplexer that multiplexes N optical channels received from the OLT-side optical transmitter and transmits them to the ONU side; M ONU-side variable optical receivers that receive L channels in one cycle and select one of the received channels by varying the wavelength; at least one second multiplexer / demultiplexer that separates N optical signals received from the first multiplexer / demultiplexer into at least two groups, wherein the number of channels included in each of the at least two groups is demultiplexed to be less than or equal to L channels; and an optical splitter that is connected to each separated group and branches the channels for each separated group to M ONU-side variable optical receivers.

[0019] In the case where N optical signals are 8 channels and L channels are 4 channels, the second multiplexer / demultiplexer performs demultiplexing to separate the 8 channels into a first group having 4 channels and a second group having 4 channels, which is less than or equal to L channels, and the optical splitter may include a first optical splitter that branches the 4-channel signal corresponding to the first group to M1 ONU-side variable optical receivers corresponding to the first group, and a second optical splitter that branches the 4-channel signal corresponding to the second group to M2 ONU-side variable optical receivers corresponding to the second group.

[0020] In the case where N optical signals are 8 channels and L channels are 4 channels, the second multiplexer / demultiplexer performs demultiplexing to separate the 8 channels into a first group having 2 channels, a second group having 2 channels, a third group having 2 channels, and a fourth group having 2 channels, wherein the optical splitter comprises a first optical splitter that branches the 2-channel signal corresponding to the first group to M1 ONU-side variable optical receivers corresponding to the first group, a second optical splitter that branches the 2-channel signal corresponding to the second group to M2 ONU-side variable optical receivers corresponding to the second group, and a third optical splitter that branches the 2-channel signal corresponding to the third group to M3 ONU-side variable optical receivers corresponding to the third group. and may include a fourth optical splitter that branches the 2-channel signal corresponding to the fourth group to each of the M4 ONU-side variable optical receivers corresponding to the fourth group.

[0021] In the case where the above N optical signals are 8 channels and the above L channels are 4 channels, the second multiplexer / demultiplexer performs demultiplexing to separate the 8 channels into a first group having 6 channels (more than L channels) and a second group having 2 channels (less than L channels), and further includes a third multiplexer / demultiplexer that performs demultiplexing to separate the 6 channels of the first group into a first-1 group having 4 channels (less than L channels) and a first-2 group having 2 channels; and the optical splitter comprises a first optical splitter that branches the 4-channel signal corresponding to the first-1 group to each of M1 ONU-side variable optical receivers corresponding to the first-1 group, and a second optical splitter that branches the 2-channel signal corresponding to the first-2 group to each of M2 ONU-side variable optical receivers corresponding to the first-2 group. and may include a third optical splitter that branches the 2-channel signal corresponding to the second group to each of the M3 ONU-side variable optical receivers corresponding to the second group.

[0022] In the case where N optical signals are 8 channels and L channels are 4 channels, the second multiplexer / demultiplexer further includes a third multiplexer / demultiplexer that performs demultiplexing by separating the 8 channels into a first group having 6 channels (L or more) and a second group having 2 channels (L or fewer), and performs demultiplexing by separating the 6 channels of the first group into a 1-1 group having 4 channels (L or more) and a 1-2 group having 1 channel (L or fewer), and further includes a fourth multiplexer / demultiplexer that performs demultiplexing by separating the 5 channels of the 1-1 group into a 1-1-1 group having 3 channels (L or fewer) and a 1-1-2 group having 2 channels (L or fewer), and the optical splitter [receives] a 3-channel signal corresponding to the 1-1-1 group It may include a first optical splitter that branches each to M1 ONU-side variable optical receivers corresponding to the first-1-1 group, a second optical splitter that branches each to M2 ONU-side variable optical receivers corresponding to the first-1-2 group, a third optical splitter that branches each to M3 ONU-side variable optical receivers corresponding to the first-2 group, and a fourth optical splitter that branches each to M4 ONU-side variable optical receivers corresponding to the second group.

[0023] An optical network system having a multiplexer / demultiplexer and an optical splitter further includes an OLT-side optical receiver that receives N optical signals from the ONU side, and the first multiplexer / demultiplexer can demultiplex the N optical signals received from the ONU side through the second multiplexer / demultiplexer and transmit them to the OLT-side optical receiver.

[0024] According to the present invention, by using a multiplexer / demultiplexer and an optical splitter, multiple channels are not all received by the optical receiver, and are separated into channels within a range that the optical receiver can receive in one cycle, thereby having the effect of using the same optical receiver instead of using different optical receivers for each multiple channel.

[0025] FIG. 1 is a drawing for illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to an embodiment of the present invention.

[0026] FIG. 2 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a first embodiment of the present invention.

[0027] FIG. 3 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a second embodiment of the present invention.

[0028] FIG. 5 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a third embodiment of the present invention.

[0029] FIG. 6 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a fourth embodiment of the present invention.

[0030] Hereinafter, specific details for implementing the invention will be described in detail with reference to the attached drawings.

[0031]

[0032] FIG. 1 is a drawing for illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to an embodiment of the present invention.

[0033] Referring to FIG. 1, an optical network system having a multiplexer / demultiplexer and an optical distributor may include an Optical Line Terminal (OLT; 100) and an Optical Network Unit (ONU; 200). In this embodiment, for convenience of explanation, the Optical Line Terminal (100) and the Optical Network Unit (200) are separated and the configurations included in each device are described and explained separately; however, the location and number of each component are not limited to the description and drawings, and various changes are possible as long as the function is maintained.

[0034] The optical line termination device (OLT) (100) may include an OLT-side optical transmitter (110), an OLT-side optical receiver (120), and a first multiplexer / demultiplexer (130).

[0035] The OLT-side optical transmitter (110) (Tx1 ~ TxN) has N optical channels (λ1λ2λ3λ4λ5λ) with different wavelengths 6 … λ N ) can be transmitted to the optical subscriber unit (ONU) side. For example, the OLT-side optical transmitter (110) (Tx1 ~ TxN) can transmit N optical channels (λ1λ2λ3λ4λ5λ) having different wavelengths. 6 … λ N The ) can be transmitted to the first multiplexer / demultiplexer (130), and the first multiplexer / demultiplexer (130) can multiplex and transmit to the optical subscriber device (ONU).

[0036] The OLT-side optical receiver (120) (Rx1 ~ RxN) has N optical signals (λ 1' λ 2' λ 3' λ 4' λ 5' λ 6' … λ N' ) can be received from the optical subscriber device (ONU) side. For example, the first multiplexer / demultiplexer (130) receives N optical signals (λ) from the optical subscriber device (ONU) side. 1' λ2' λ 3' λ 4' λ 5' λ 6' … λ N' It receives ) and demultiplexes it, then transmits it to the OLT-side optical receivers (120) (Rx1 ~ RxN). The OLT-side optical receivers (120) (Rx1 ~ RxN) receive N optical signals (λ) demultiplexed from the first multiplexer / demultiplexer (130). 1' λ 2' λ 3' λ 4' λ 5' λ 6' … λ N' Each can receive ).

[0037] The first multiplexer / demultiplexer (130) receives N optical channel signals (λ1λ2λ3λ4λ5λ) from the OLT-side optical transmitter (110). 6 … λ N )(300) can be multiplexed and transmitted to the optical subscriber device (ONU).

[0038] The first multiplexer / demultiplexer (130) receives N optical channel signals (λ) from the optical subscriber device (ONU) side through the second multiplexer / demultiplexer (230). 1' λ 2' λ 3' λ 4' λ 5' λ 6' … λ N' )(310) can be demultiplexed and transmitted to the OLT-side optical receiver (110).

[0039]

[0040] The optical subscriber device (ONU) (200) includes a variable ONU (210, 220), a second multiplexer / demultiplexer (230), and an optical splitter (240, 250).

[0041] The variable ONU (210, 220) includes an ONU-side variable optical receiver (not shown) and an ONU-side variable optical transmitter (not shown).

[0042] The ONU-side variable optical receiver can receive L channels in one cycle. The ONU-side variable optical receiver is a wavelength-tunable receiver capable of selecting one of the received channels by varying the wavelength. For example, the received channel can be changed / selected according to the wavelength that changes according to temperature changes caused by a heater, TEC, etc.

[0043] The ONU-side variable optical transmitter (210, 220) has an optical channel (λ) corresponding to the channel received from the optical splitter (240, 250). 1' λ 2' λ 3' λ 4' λ 5' λ 6' … λ N' ) can be generated and transmitted to the Optical Circuit Termination (OLT) side. For example, the transmitted channel can be changed / selected according to the wavelength that changes according to the temperature change caused by a heater, TEC, etc. For example, the ONU-side variable optical transmitter (210) can transmit an optical channel signal (λ 1' λ 2' λ 3' λ 4' One of the channels is selected, and an optical signal is transmitted to the optical splitter (240) through the selected channel, and the optical splitter (240) can transmit the optical signal to the second multiplexer / demultiplexer (230).

[0044] The second multiplexer / demultiplexer (230) receives N optical signals (λ1λ2λ3λ4λ5λ) from the first multiplexer / demultiplexer (130). 6 … λ N The signals can be demultiplexed by separating them into at least two groups. For example, the second multiplexer / demultiplexer (230) can separate N optical signals received from the first multiplexer / demultiplexer (130) into various groups such as (1) a first group and a second group, (2) a first group, a second group and a third group, (4) a first group, a second group, a third group and a fourth group, etc.

[0045] The number of channels included in the separated groups of the second multiplexer / demultiplexer (230) can be selected / set to be less than L channels that the ONU-side variable optical receiver can receive in one cycle.

[0046] The second multiplexer / demultiplexer (230) uses an optical channel signal (λ) through an optical splitter (240, 250). 1' λ 2' λ 3' λ 4' λ 5' λ 6' … λ N' ) is multiplexed and sent to the first multiplexer / demultiplexer (230).

[0047] Optical splitters (240, 250) may be provided for each group separated by the second multiplexer / demultiplexer (230). The optical splitters (240, 250) may branch the channels for each separated group to M ONU-side variable optical receivers. For example, the first optical splitter (240) is for the first group (λ1λ2λ3λ 4) The optical signals (λ1λ2λ3λ4) of the separated channels are connected to and can be branched to M ONU-side variable optical receivers (210). Accordingly, each ONU-side variable optical receiver (210) can receive the optical signals (λ1λ2λ3λ4). The second optical splitter (250) is connected to the second group (λ1λ2λ3λ4) and the optical signals (λ4λ5λ) of the separated channels 6 … λ N ) can be branched to M ONU-side variable optical receivers (210). Accordingly, each ONU-side variable optical receiver (220) has an optical signal (λ4λ5λ 6 … λ N Can receive ).

[0048] The following will be explained in detail using specific embodiments.

[0049]

[0050] FIG. 2 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a first embodiment of the present invention.

[0051] Referring to FIGS. 1 and FIGS. 2, the first embodiment is described based on the case where N optical signals on the side of the optical line termination device (1000) are 8 channels and L channels are 4 channels, but these figures are for illustrative purposes only and can be changed in various ways, and parts already explained in FIGS. 1 will be omitted.

[0052] The second multiplexer / demultiplexer (2030) can perform demultiplexing to separate 8 channels (λ1λ2λ3λ4λ5λ6λ7λ8) into a first group (λ1λ2λ3λ4) and a second group (λ5λ6λ7λ8).

[0053] At this time, the second multiplexer / demultiplexer (2030) can make the number of channels transmitted to the first group (λ1λ2λ3λ4) and the second group (λ5λ6λ7λ8) less than or equal to L channels ('4') that the ONU-side variable optical receiver can receive in one cycle.

[0054] The first optical splitter (2040) can split the 4-channel signal (λ1λ2λ3λ4) corresponding to the first group into M1 ONU-side variable optical receivers (2010) corresponding to the first group. That is, the 4-channel signal (λ1λ2λ3λ4) can be received by each ONU-side variable optical receiver (2010). The ONU-side variable optical receiver (2010) can select any one of the 4-channel signals (λ1λ2λ3λ4) and use it for communication.

[0055] The second optical splitter (2050) can split the 4-channel signal (λ5λ6λ7λ8) corresponding to the second group into M2 ONU-side variable optical receivers (2020) corresponding to the second group. That is, the 4-channel signal (λ5λ6λ7λ8) can be received by each ONU-side variable optical receiver (2020). The ONU-side variable optical receiver (2020) can select any one of the 4-channel signals (λ5λ6λ7λ8) and use it for communication.

[0056]

[0057] In this way, a second multiplexer / demultiplexer (2030) is provided in front of the optical splitter (2040, 2050), and by ensuring that the group separated by the second multiplexer / demultiplexer (2030) is less than or equal to 'L channels that the ONU-side variable optical receiver can receive in one cycle,' M ONU-side variable optical receivers can have the same structure ('structure for receiving L channels'). In other words, if the role of the second multiplexer / demultiplexer (2030) is not performed, there is a problem that different forms of ONU-side variable optical receivers must be used, such as a structure for receiving 10 channels, a structure for receiving 7 channels, a structure for receiving 4 channels, etc.

[0058]

[0059] FIG. 3 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a second embodiment of the present invention.

[0060] Referring to FIG. 1 and FIG. 3, the second embodiment is described based on the case where N optical signals on the optical line termination device (1100) side are 8 channels and L channels are 4 channels, but these figures are for illustrative purposes only and can be changed in various ways.

[0061] The second multiplexer / demultiplexer (2130) has 8 channels (λ1λ2λ3λ4λ5λ6λ7λ8) in the first group (λ1λ2), the second group ( Demultiplexing can be performed to separate into λ3λ4), the third group (λ5λ6) and the fourth group (λ7λ8).

[0062] At this time, the second multiplexer / demultiplexer (2130) is the first group (λ1λ2), the second group ( The number of channels transmitted to the third group (λ3λ4), the third group (λ5λ6), and the fourth group (λ7λ8) can be made to be less than or equal to L channels ('4') that the ONU-side variable optical receiver can receive in one cycle.

[0063] The first optical splitter (2140) can split the 2-channel signal (λ1λ2) corresponding to the first group into M1 ONU-side variable optical receivers corresponding to the first group. That is, the 2-channel signal (λ1λ2) can be received by each ONU-side variable optical receiver.

[0064] The second optical splitter (2150) can split the 2-channel signal (λ3λ4) corresponding to the second group into M2 ONU-side variable optical receivers corresponding to the second group. That is, the 2-channel signal (λ3λ4) can be received by each ONU-side variable optical receiver.

[0065] The third optical splitter (2160) can split the 2-channel signal (λ5λ6) corresponding to the third group into M3 ONU-side variable optical receivers corresponding to the third group. That is, the 2-channel signal (λ5λ6) can be received by each ONU-side variable optical receiver.

[0066] The fourth optical splitter (2170) can split the 2-channel signal (λ7λ8) corresponding to the third group into M4 ONU-side variable optical receivers corresponding to the fourth group. That is, the 2-channel signal (λ7λ8) can be received by each ONU-side variable optical receiver.

[0067]

[0068] FIG. 5 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a third embodiment of the present invention.

[0069] Referring to FIGS. 1 and FIGS. 5, the third embodiment is described based on the case where N optical signals on the optical line termination device (1200) side are 8 channels and L channels are 4 channels, but these figures are for illustrative purposes only and can be changed in various ways.

[0070] The second multiplexer / demultiplexer (2230) can demultiplexe the 8 channels (λ1λ2λ3λ4λ5λ6λ7λ8) into a first group (λ1λ2λ3λ4λ5λ6) having 6 channels, which is more than L channels ('4') and a second group (λ7λ8) having 2 channels, which is less than L channels.

[0071] The third multiplexer / demultiplexer (2240) separates the channels once more to reduce them to L channels ('4') or fewer because the first group (λ1λ2λ3λ4λ5λ6) has 6 channels, which is more than L channels ('4').

[0072] The third multiplexer / demultiplexer (2240) has 6 channels of the first group (λ1λ2λ3λ4λ5λ6), 4 channels (λ1λ2λ3λ4) which is less than or equal to L channels, and 2 channels ( Demultiplexing can be performed to separate into 1st and 2nd groups having λ5λ6).

[0073] The first optical splitter (2250) can split the 4-channel signals (λ1λ2λ3λ4) corresponding to the 1-1 group into M1 ONU-side variable optical receivers corresponding to the 1-1 group.

[0074] The second optical splitter (2260) can split the 2-channel signal (λ5λ6) corresponding to the first-2 group into M3 ONU-side variable optical receivers corresponding to the first-2 group.

[0075] The third optical splitter (2270) can branch the 2-channel signal (λ7λ8) corresponding to the second group to each of the M ONU-side variable optical receivers.

[0076]

[0077] FIG. 6 is a diagram illustrating an optical network system having a multiplexer / demultiplexer and an optical splitter according to a fourth embodiment of the present invention.

[0078] Referring to FIG. 1 and FIG. 6, the fourth embodiment is described based on the case where N optical signals on the optical line termination device (1300) side are 8 channels and L channels are 4 channels, but these figures are for illustrative purposes only and can be changed in various ways.

[0079] The second multiplexer / demultiplexer (2330) can demultiplexe the 8 channels (λ1λ2λ3λ4λ5λ6λ7λ8) into a first group (λ1λ2λ3λ4λ5λ6) having 6 channels, which is more than L channels ('4') and a second group (λ7λ8) having 2 channels, which is less than L channels.

[0080] The third multiplexer / demultiplexer (2340) separates the channels once more to reduce them to L channels ('4') or fewer because the first group (λ1λ2λ3λ4λ5λ6) has 6 channels, which is more than L channels ('4').

[0081] The third multiplexer / demultiplexer (2340) has 6 channels of the first group (λ1λ2λ3λ4λ5λ6) and 4 channels (λ1λ2λ3λ4λ5) which are less than or equal to L channels, and 1 channel ( Demultiplexing can be performed to separate into 1st and 2nd groups having λ6).

[0082] The fourth multiplexer / demultiplexer (2350) separates the channels once more to reduce them to L channels ('4') or fewer because the first-1 group (λ1λ2λ3λ4λ5) has 6 channels, which is more than L channels ('4').

[0083] The fourth multiplexer / demultiplexer (2350) can demultiplexe by separating the 5 channels of the 1-1 group (λ1λ2λ3λ4λ5) into a 1-1-1 group (λ1λ2λ3) having 3 channels, which is less than or equal to L channels, and a 1-1-2 group (λ4λ5) having 2 channels, which is less than or equal to L channels.

[0084] The first optical splitter (2360) can split the 3-channel signal (λ1λ2λ3) corresponding to the 1-1-1 group into M1 ONU-side variable optical receivers corresponding to the 1-1-1 group.

[0085] The second optical splitter (2370) can split the 2-channel signal (λ4λ5) corresponding to the first-1-2 group into M2 ONU-side variable optical receivers corresponding to the first-1-2 group.

[0086] The third optical splitter (2380) is a 1-channel signal corresponding to the 1st-2nd group ( λ6) can be branched to M3 ONU-side variable optical receivers corresponding to the 1st and 2nd groups, respectively. Here, when only one channel signal is received by the optical receiver, the corresponding M optical subscriber devices (ONU) (2400) can allocate channels using a time division multiplexing (TDM) method.

[0087] The fourth optical splitter (2390) can split the 2-channel signal (λ7λ8) corresponding to the second group into M4 ONU-side variable optical receivers corresponding to the second group.

[0088]

[0089] The described embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

[0090] Furthermore, it should be noted that the embodiments are for illustrative purposes only and are not intended to be limiting. Additionally, a person skilled in the art will understand that various embodiments are possible within the scope of the technical concept of the present invention.

Claims

1. An OLT-side optical transmitter that transmits N optical channels having different wavelengths to the ONU side; A first multiplexer / demultiplexer that multiplexes N optical channels received from the OLT-side optical transmitter and transmits them to the ONU side; M ONU-side variable optical receivers that receive L channels in one cycle and select one of the received channels by varying the wavelength; At least one second multiplexer / demultiplexer that separates N optical signals received from the first multiplexer / demultiplexer into at least two groups, wherein the number of channels included in each of the at least two groups is demultiplexed to be L channels or less; and An optical network system having a multiplexer / demultiplexer and an optical splitter, comprising: an optical splitter that is connected to each separated group and branches the channels for each separated group to each ONU-side variable optical receiver.

2. In Paragraph 1, In the case where the above N optical signals are 8 channels and the above L channels are 4 channels, The above-mentioned second multiplexer / demultiplexer is, Demultiplexing is performed to separate the above 8 channels into a first group having 4 channels and a second group having 4 channels, wherein the above L channels or fewer are separated, and The above-mentioned optical splitter is, A first optical splitter that branches a 4-channel signal corresponding to the first group to each of M1 ONU-side variable optical receivers corresponding to the first group; and An optical network system having a multiplexer / demultiplexer and an optical splitter, comprising a second optical splitter that branches a 4-channel signal corresponding to the second group to each of the M2 ONU-side variable optical receivers corresponding to the second group.

3. In Paragraph 1, In the case where the above N optical signals are 8 channels and the above L channels are 4 channels, The above-mentioned second multiplexer / demultiplexer is, Demultiplexing is performed to separate the above 8 channels into a first group having 2 channels, a second group having 2 channels, a third group having 2 channels, and a fourth group having 2 channels, wherein the above 8 channels are less than or equal to L channels. The above-mentioned optical splitter is, A first optical splitter that branches a 2-channel signal corresponding to the first group to each of M1 ONU-side variable optical receivers corresponding to the first group; A second optical splitter that branches a 2-channel signal corresponding to the second group to each of the M2 ONU-side variable optical receivers corresponding to the second group; A third optical splitter that branches a 2-channel signal corresponding to the third group to each of the M3 ONU-side variable optical receivers corresponding to the third group; and An optical network system having a multiplexer / demultiplexer and an optical splitter, comprising a fourth optical splitter that branches a 2-channel signal corresponding to the fourth group to each of the M4 ONU-side variable optical receivers corresponding to the fourth group.

4. In Paragraph 1, In the case where the above N optical signals are 8 channels and the above L channels are 4 channels, The above-mentioned second multiplexer / demultiplexer is, Demultiplexing is performed to separate the above 8 channels into a first group having 6 channels, which is L channels or more, and a second group having 2 channels, which is L channels or less. It further includes a third multiplexer / demultiplexer that performs demultiplexing to separate the 6 channels of the first group into a 1-1 group having 4 channels and a 1-2 group having 2 channels, wherein the 6 channels of the first group are less than or equal to the L channels. The above-mentioned optical splitter is, A first optical splitter that branches a 4-channel signal corresponding to the above 1-1 group to each of M1 ONU-side variable optical receivers corresponding to the above 1-1 group; A second optical splitter that branches a 2-channel signal corresponding to the first and second groups to each of M2 ONU-side variable optical receivers corresponding to the first and second groups; and An optical network system having a multiplexer / demultiplexer and an optical splitter, comprising a third optical splitter that branches a 2-channel signal corresponding to the second group to each of the M3 ONU-side variable optical receivers corresponding to the second group.

5. In Paragraph 1, In the case where the above N optical signals are 8 channels and the above L channels are 4 channels, The above-mentioned second multiplexer / demultiplexer is, Demultiplexing is performed to separate the above 8 channels into a first group having 6 channels, which is L channels or more, and a second group having 2 channels, which is L channels or less. It further includes a third multiplexer / demultiplexer that performs demultiplexing to separate the 6 channels of the first group into a 1-1 group having 4 channels, which is L or more, and a 1-2 group having 1 channel, which is L or fewer. It further includes a fourth multiplexer / demultiplexer that performs demultiplexing by separating the 5 channels of the above 1-1 group into a 1-1-1 group having 3 channels, which is less than or equal to L channels, and a 1-1-2 group having 2 channels, which is less than or equal to L channels. The above-mentioned optical splitter is, A first optical splitter that branches a 3-channel signal corresponding to the above 1-1-1 group to each of M1 ONU-side variable optical receivers corresponding to the above 1-1-1 group; A second optical splitter that branches a 2-channel signal corresponding to the above 1-1-2 group to each of M2 ONU-side variable optical receivers corresponding to the above 1-1-2 group; A third optical splitter that branches a 1-channel signal corresponding to the first-2 groups to each of the M3 ONU-side variable optical receivers corresponding to the first-2 groups; and An optical network system having a multiplexer / demultiplexer and an optical splitter, comprising a fourth optical splitter that branches a 2-channel signal corresponding to the second group to each of the M4 ONU-side variable optical receivers corresponding to the second group.

6. In Paragraph 1, It further includes an OLT-side optical receiver that receives N optical signals from the ONU side, and The first multiplexer / demultiplexer is, An optical network system having a multiplexer / demultiplexer and an optical splitter, which demultiplexes N optical signals received from the ONU side through the second multiplexer / demultiplexer and transmits them to the OLT side optical receiver.

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