Optical communication system, base station and communication method

Abstract

Provided is an optical communication system in which an aggregation station and a plurality of branch stations are connected in series with the aggregation station at the head. Each of the plurality of branch stations demultiplexes a signal received from equipment on the respective upstream side into a first demultiplexed signal having a wavelength allocated to the respective branch station and into a second demultiplexed signal having another wavelength; transmits the second demultiplexed signal to respective equipment on the downstream side; multiplexes a signal received from the respective equipment on the downstream side with the signal processed by the respective branch station; and transmits the resultant signal to the respective equipment on the upstream side.

Description

[Technical Field]

[0001] The present invention relates to an optical communication system, a base station, and a communication method. [Background technology]

[0002] Millimeter-wave radio waves have attracted attention due to their potential for high-speed transmission. However, because millimeter-wave radio waves have large propagation losses, they require the deployment of wireless base stations at high density.

[0003] As a method for deploying wireless base stations, Non-Patent Document 1 discloses a method of applying analog RoF (Radio-over-Fiber). Analog RoF is a technology in which an optical signal is intensity-modulated with a wireless signal and the intensity-modulated optical signal is transmitted over an optical fiber, and the original wireless signal can be extracted by O / E converting the transmitted optical signal.

[0004] By applying analog RoF, wireless base stations can be separated into a central station that performs signal processing and a base station that has antenna functions, and the signal processing function can be consolidated in the central station, which simplifies the base station and makes it easier to install.

[0005] Non-Patent Document 2 discloses that the central station and the base stations are connected in a cascade configuration in order to more easily deploy the base stations. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Kodai Ito, Mizuki Suga, Hirofumi Shirato, Naoki Kita, Takeshi Onisawa, "Efficient Accommodation of Diverse High-Frequency Band Wireless Systems Using Analog Radio Fiber," NTT Technical Journal, 32(3), 15-17, 2020. [Non-patent document 2] E. -S. Kim, M. Sung, JH Lee, JK Lee, S. -H. Cho and J. Kim, "Coverage Extension of Indoor 5G Network Using RoF-Based Distributed Antenna System," IEEE Access, vol. 8, pp. 194992-194999, 2020. Summary of the Invention [Problem to be solved by the invention]

[0007] The base station described in Non-Patent Document 2 divides an optical signal using an optical splitter, then splits the optical signal to extract an optical signal of a desired wavelength. However, the optical splitter causes loss in the optical signal, which can reduce the amplitude of the optical signal received by a base station far from the central station. The present invention provides an optical communication system, a base station, and a communication method that can reduce loss of an optical signal. [Means for solving the problem]

[0008] One aspect of the present invention is an optical communication system in which a central station and multiple base stations are connected in series with the central station at the head, and the multiple base stations demultiplex a signal received from an upstream device into a first demultiplexed signal of a wavelength assigned to the station and a second demultiplexed signal of another wavelength, transmit the second demultiplexed signal to the downstream device, combine the signal received from the downstream device with a signal processed by the station, and transmit the combined signal to the upstream device.

[0009] One aspect of the present invention is a base station in an optical communication system in which a central station and multiple base stations are connected in series with the central station at the head, and the base station demultiplexes a signal received from an upstream device into a first demultiplexed signal of a wavelength assigned to the station and a second demultiplexed signal of another wavelength, transmits the second demultiplexed signal to the downstream device, combines the signal received from the downstream device with a signal processed by the station, and transmits the combined signal to the upstream device.

[0010] A communication method for a base station in an optical communication system in which a central station and multiple base stations are connected in series with the central station at the head, the communication method for a base station comprising the steps of: demultiplexing a signal received from an upstream device into a first demultiplexed signal of a wavelength assigned to the station and a second demultiplexed signal of another wavelength, and transmitting the second demultiplexed signal to a downstream device; and combining the signal received from the downstream device with a signal processed by the station, and transmitting the combined signal to the upstream device. [Effects of the Invention]

[0011] The optical communication system, base station, and communication method according to the present invention can reduce loss of optical signals. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an optical communication system in which a central station and a base station are connected in a cascade configuration. [Figure 2] FIG. 2 is a diagram illustrating a configuration of a central station according to the first embodiment. [Figure 3] 1 is a diagram illustrating a configuration of an ith base station (i is an integer satisfying 1≦i≦N) according to the first embodiment. [Figure 4] 10 is a flowchart showing a transmission method of the aggregation station. [Figure 5] 10 is a flowchart showing a receiving method of the aggregation station. [Figure 6] 10 is a flowchart showing a method of communication between a base station and an upstream device. [Figure 7] 10 is a flowchart showing a method of communication between a base station and a downstream device. [Figure 8] FIG. 10 is a diagram illustrating a configuration of a central station according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a configuration of an ith base station (i is an integer satisfying 1≦i≦N) according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Optical communication system First Embodiment FIG. 1 is a diagram showing the configuration of an optical communication system 1 in which an aggregation station 10 and a base station 11 are connected in a cascade configuration. The optical communication system 1 has one aggregation station 10 and N base stations 11 (N is an integer equal to or greater than 2). In the optical communication system 1, the aggregation station 10 is at the head, and the N base stations 11 are connected in series. Hereinafter, when distinguishing between the N base stations 11, each base station 11 will be referred to as the i-th base station 11-i (i is an integer satisfying 1≦i≦N). However, when describing features common to all the i-th base stations 11-i, the base station 11 will simply be referred to as the base station 11. Note that the ordinal number i is equal to the number of hops from the aggregation station 10. In the optical communication system 1, the direction from the aggregation station 10 to the base station 11 is referred to as downstream, and the direction from the base station 11 to the aggregation station 10 is referred to as upstream.

[0014] The central station 10 performs E / O conversion on the generated wireless signal and transmits the generated downstream optical signal to the first base station 11-1. The first base station 11-1 demultiplexes the received downstream optical signal, transmits some of the optical signals to the second base station 11-2, processes the remaining optical signal within itself, and transmits a wireless signal according to the optical signal. The first base station 11-1, for example, radiates the wireless signal obtained by O / E conversion of the optical signal into space via an antenna. The second base station 11-2 to the N-1th base station 11-(N-1) also perform the same operation as the first base station 11-1. In other words, the ith base station 11-i (i is an integer satisfying 2≦i≦N−1) demultiplexes the optical signal received from the i-1th base station 11-(i-1), which is an upstream device, and transmits some of the optical signals to the i+1th base station 11-(i+1), which is a downstream device.

[0015] The ith base station 11-i (i is an integer satisfying 2≦i≦N−1) generates an upstream optical signal by E / O converting a radio signal received via an antenna, for example. The ith base station 11-i combines the optical signal received from a downstream device with the upstream optical signal and transmits the combined optical signal to an upstream device. In other words, the ith base station 11-i combines the optical signal received from the (i+1) base station 11-(i+1) with an optical signal converted from a radio signal received by the ith base station, and transmits the combined optical signal to the (i−1) base station 11-(i−1).

[0016] That is, the optical signal transmitted from the central station 10 travels downstream through the first base station 11-1 and the second base station 11-2, and finally reaches the Nth base station 11-N. The optical signal transmitted from the Nth base station 11-N travels upstream to the N-1th base station 11-(N-1), and finally reaches the central station 10. The central station 10 performs O / E conversion on the received optical signal to obtain a radio signal. The radio signal is subjected to, for example, signal processing.

[0017] As described above, in the optical communication system 1, N base stations 11 are connected in series with the central station 10 at the head. Radio signals received at the base stations 11 are converted into optical signals without undergoing signal processing at the base stations 11 and are then aggregated at the central station 10. The optical signals aggregated by the central station 10 are converted into radio signals, and the radio signals received at the base stations 11 are extracted. Because the base stations 11 do not need to include a configuration for processing radio signals, the base stations 11 can be easily implemented.

[0018] The central station 10 and the first base station 11-1, and the i-th base station 11-i and the i+1-th base station 11-(i+1) (i is an integer satisfying 1≦i≦N−1) are connected by two transmission paths, a downstream transmission path 12 and an upstream transmission path 13. The transmission paths are, for example, optical fibers.

[0019] 2 is a diagram showing the configuration of the central station 10 according to the first embodiment. The central station 10 includes a transmitting unit 100, an E / O converting unit 101, a multiplexing unit 102, a demultiplexing unit 103, an O / E converting unit 104, and a receiving unit 105. The central station 10 includes N units of each of the transmitting units 100, the E / O converting units 101, the O / E converting units 104, and the receiving units 105, the number of which is the same as the number of base stations 11.

[0020] The transmitting units 100 are referred to as a first transmitting unit 100-1, a second transmitting unit 100-2, etc., and an N-th transmitting unit 100-N. The E / O converting units 101 are referred to as a first E / O converting unit 101-1, a second E / O converting unit 101-2, etc., and an N-th E / O converting unit 101-N. The O / E converting units 104 are referred to as a first O / E converting unit 104-1, a second O / E converting unit 104-2, etc., and an N-th O / E converting unit 104-N. The receiving units 105 are referred to as a first receiving unit 105-1, a second receiving unit 105-2, etc., and an N-th receiving unit 105-N.

[0021] The i-th transmitter 100-i (i is an integer satisfying 1≦i≦N) transmits an electrical signal to the i-th E / O converter 101-i. The i-th E / O converter 101-i (i is an integer satisfying 1≦i≦N) converts the received electrical signal into an optical signal and transmits the optical signal to the multiplexer 102. The wavelengths of the optical signals transmitted from the i-th E / O converter 101-i to the multiplexer 102 are different from each other. The wavelength of the optical signal transmitted from the i-th E / O converter 101-i is λ DLi and differs for each E / O converter 101. The optical signal transmitted by the i-th E / O converter 101-i is intended to ultimately reach the i-th base station 11-i. The central station 10 can switch the base station 11 to which the transmitted optical signal will ultimately reach by switching which transmitter 100 to use to transmit the electrical signal. This allows the central station 10 to perform handover and switch whether the base station 11 transmits or receives signals.

[0022] The multiplexing unit 102 multiplexes the optical signals received from the E / O converting unit 101 and transmits the multiplexed optical signals to the first base station 11-1. The demultiplexing unit 103 demultiplexes the optical signals received from the first base station 11-1 and transmits the demultiplexed optical signals to the O / E converting unit 104. The wavelength of the optical signal transmitted by the demultiplexing unit 103 to the i-th O / E converting unit 104-i is λ ULi and differs for each O / E conversion unit 104. ULi The optical signal is an optical signal transmitted from the i-th base station 11-i.

[0023] The i-th O / E converter 104-i (i is an integer satisfying 1≦i≦N) converts the received optical signal into an electrical signal and transmits the electrical signal to the i-th receiver 105-i. The i-th receiver 104-5 (i is an integer satisfying 1≦i≦N) receives the electrical signal from the i-th O / E converter 104-i.

[0024] The aggregation station 10 and the first base station 11-1 are connected by two transmission paths: a downstream transmission path 12-1 and an upstream transmission path 13-1. The downstream transmission path 12-1 is connected to a multiplexing unit 102 and transmits an optical signal multiplexed by the multiplexing unit 102 to the first base station 11-1. The upstream transmission path 13-1 is connected to a demultiplexing unit 103 and transmits an optical signal from the first base station 11-1 to the demultiplexing unit 103.

[0025] 3 is a diagram showing the configuration of the ith base station 11-i (i is an integer satisfying 1≦i≦N) according to the first embodiment. The ith base station 11-i includes an ith demultiplexing unit 111-i, an ith O / E conversion unit 112-i, an ith transmitting amplifier 113-i, an ith circulator 114-i, an ith antenna 115-i, an ith receiving amplifier 116-i, an ith E / O conversion unit 117-i, and an ith multiplexing unit 118-i. Like the i-th base station 11-i, the i-th demultiplexing unit 111-i, the i-th O / E conversion unit 112-i, the i-th transmitting amplifier 113-i, the i-th circulator 114-i, the i-th antenna 115-i, the i-th receiving amplifier 116-i, the i-th E / O conversion unit 117-i, and the i-th multiplexing unit 118-i will also be referred to as the demultiplexing unit 111, the O / E conversion unit 112, the transmitting amplifier 113, the circulator 114, the antenna 115, the i-th receiving amplifier 116, the E / O conversion unit 117, and the multiplexing unit 118, respectively, when explaining the characteristics that are independent of the position of the base station 11.

[0026] The i-th demultiplexing unit 111-i demultiplexes the wavelength λ 1 received from the upstream device via the downstream transmission line 12-i. DLi The ith demultiplexing unit 111-i demultiplexes the optical signal of wavelength λ into an optical signal of wavelength λ and an optical signal of other wavelengths. DLi The optical signal of this wavelength is transmitted to the i-th O / E converter 112-i via the downstream transmission path 12-(i+1), and the optical signals of the other wavelengths are transmitted to the i+1-th base station 11-(i+1).

[0027] The i-th O / E converter 112-i converts the optical signal received from the i-th demultiplexer 111-i into an electrical signal and transmits it to the i-th transmitting amplifier 113-i. The i-th transmitting amplifier 113-i amplifies the electrical signal received from the i-th O / E converter 112-i and transmits the amplified electrical signal to the i-th circulator 114-i.

[0028] The i-th circulator 114-i transmits the electrical signal received from the i-th transmitting amplifier 113-i to the i-th antenna 115-i, and also transmits the electrical signal received from the i-th antenna 115-i to the i-th receiving amplifier 116-i.

[0029] The i-th antenna 115-i radiates the electrical signal received from the i-th circulator 114-i into space, and also transmits the received electrical signal to the i-th circulator 114-i.

[0030] The i-th receiving amplifier 116-i amplifies the electrical signal received from the i-th circulator 114-i and transmits the amplified electrical signal to the i-th E / O converter 117-i. The i-th E / O converter 117-i converts the electrical signal received from the i-th receiving amplifier 116-i into an electrical signal having a wavelength λ ULi and transmits it to the ith multiplexer 118-i.

[0031] The ith multiplexer 118-i multiplexes the optical signal received from the ith E / O converter 117-i with the optical signal received from the (i+1)th base station 11-(i+1) via the upstream transmission path 13-(i+1), and transmits the multiplexed optical signal to an upstream device via the upstream transmission path 13-i. The first multiplexer 118-1 transmits the multiplexed optical signal to the aggregation station 10, and the ith multiplexer 118-i (i is an integer satisfying 2≦i≦N−1) transmits the multiplexed optical signal to the (i−1)th base station 11-(i−1).

[0032] The i-th demultiplexing unit 111-i and the i-th multiplexing unit 118-i are, for example, thin film filters or FBGs (Fiber Bragg Gratings). The i-th demultiplexing unit 111-i demultiplexes an optical signal received from an upstream device and separates the optical signal having a wavelength λ DLiThe i-th multiplexer 118-i extracts the signal of wavelength λ 1 received from the i-th E / O converter 117-i, thereby extracting the optical signal corresponding to the local station. ULi The optical signal of wavelength λ transmitted from the i+1th E / O converter 117-i is multiplexed with the optical signal transmitted from the i+1th base station 11-(i+1), and the multiplexed optical signal is transmitted to an upstream device. ULi The optical signal is finally received by the i-th receiving unit 105-i.

[0033] The N-th base station 11-N has almost the same configuration as the i-th base station 11-i (i is an integer satisfying 1≦i≦N−1), but may not include a demultiplexing unit and a multiplexing unit.

[0034] In the configuration of the base station 11, the two transmission lines connecting the base station 11 to other devices are connected to the demultiplexing unit 111 and the multiplexing unit 118.

[0035] 4 is a flowchart showing a transmission method of the aggregation station 10. The transmitter 100 transmits an electrical signal to the E / O converter 101 (step S1). The E / O converter 101 converts the electrical signal into an optical signal (step S2). The multiplexer 102 multiplexes the optical signals (step S3). The multiplexed optical signal is transmitted to the first base station 11-1.

[0036] 5 is a flowchart showing a receiving method of the aggregation station 10. The demultiplexing unit 103 demultiplexes the optical signal received from the first base station 11-1 (step S11). The O / E conversion unit 104 converts the optical signal into an electrical signal (step S12). The receiving unit 105 receives the electrical signal (step S13).

[0037] 6 is a flowchart showing a method of communication between the base station 11 and an upstream device. The demultiplexing unit 111 demultiplexes an optical signal received from the upstream device (step S21). The demultiplexed optical signal is transmitted to the O / E conversion unit 112 and the downstream device. The O / E conversion unit 112 converts the optical signal into an electrical signal (step S22). The transmission amplifier 113 amplifies the electrical signal (step S23). The electrical signal is radiated from the antenna 115 via the circulator 114 (step S24).

[0038] 7 is a flowchart showing a method of communication between the base station 11 and downstream devices. The antenna 115 receives an electrical signal (step S31). The electrical signal passes through the circulator 114 and is amplified by the receiving amplifier 116 (step S32). The E / O converter 117 converts the electrical signal into an optical signal (step S33). The multiplexer 118 multiplexes the optical signals (step S34). The multiplexed optical signal is transmitted to upstream devices.

[0039] In the optical communication system 1 according to the first embodiment, the base station 11 does not include an optical splitter, which makes it possible to reduce loss of optical signals.

[0040] In the optical communication system 1 according to the first embodiment, the wavelength of the optical signal transmitted by the transmitting unit 100 and the wavelength of the optical signal received by the receiving unit 105 may be the same.

[0041] Second Embodiment In the optical communication system 1 according to the second embodiment, the equipment in the central station 10 and the equipment in the base station 11 are connected by a single transmission path 14. That is, a signal transmitted by the base station 11 to the upstream side and a signal received from the upstream side are transmitted through the same transmission path, and a signal transmitted by the base station 11 to the downstream side and a signal received from the downstream side are transmitted through the same transmission path.

[0042] 8 is a diagram showing the configuration of a central station 10 according to the second embodiment. The central station 10 according to the second embodiment differs from the central station 10 according to the first embodiment in that it includes a multiplexing unit 106 instead of the multiplexing unit 102 and the demultiplexing unit 103. The multiplexing unit 106 multiplexes optical signals received from the E / O conversion unit 101 and transmits the multiplexed optical signals to the first base station 11-1. The multiplexing unit 106 also demultiplexes optical signals received from the first base station 11-1 and transmits the demultiplexed optical signals to the O / E conversion unit 104. The wavelength of the optical signal that the multiplexing unit 106 transmits to the i-th O / E conversion unit 104-i is λ ULi and differs for each O / E conversion unit 104. In other words, the multiplexing unit 106 functions as both the multiplexing unit 102 and the demultiplexing unit 103.

[0043] The central station 10 and the first base station 11-1 according to the second embodiment are connected by a single transmission line. The single transmission line connecting the central station 10 and the first base station 11-1 is connected to the multiplexing unit 106 in the configuration of the central station 10.

[0044] 9 is a diagram showing the configuration of the ith remote station 11-i (i is an integer satisfying 1≦i≦N) according to the second embodiment. The ith remote station 11-i according to the second embodiment includes an ith upstream circulator 110-i and an ith downstream circulator 119-i in addition to the ith remote station 11-i according to the first embodiment. Furthermore, the ith demultiplexing unit 111-i and the ith multiplexing unit 118-i according to the second embodiment differ in the connection relationship with other components from the ith demultiplexing unit 111-i and the ith multiplexing unit 118-i according to the first embodiment.

[0045] The i-th upstream circulator 110-i transmits the optical signal received from the upstream device via the transmission path 14-i to the i-th demultiplexing unit 111-i. The i-th upstream circulator 110-i transmits the optical signal received from the i-th multiplexing unit 118-i to the upstream device via the transmission path 14-i.

[0046] The i-th demultiplexing unit 111-i according to the second embodiment demultiplexes the optical signal received from the i-th upstream circulator 110-i at wavelength λ DLi The ith demultiplexing unit 111-i according to the second embodiment demultiplexes an optical signal of wavelength λ DLi The optical signal of wavelength λ is transmitted to the i-th O / E converter 112-i. DLi The optical signal that is not the i-th downstream circulator 119-i is transmitted to the i-th downstream circulator 119-i.

[0047] The i-th multiplexing unit 118-i according to the second embodiment multiplexes the optical signals transmitted from the i-th E / O conversion unit 117-i and the i-th downstream circulator 119-i, and transmits the multiplexed optical signal to the i-th upstream circulator 110-i.

[0048] The i-th downstream circulator 119-i transmits the optical signal received from the i+1th base station 11-(i+1), which is a downstream device, via the transmission path 14-(i+1), to the i-th multiplexer 118-i. The i-th downstream circulator 119-i transmits the optical signal received from the i-th demultiplexer 111-i via the transmission path 14-(i+1), to the i+1th base station 11-(i+1), which is a downstream device.

[0049] With the above configuration, the optical signal received by the ith base station 11-i from the upstream side is input to the ith demultiplexing unit 111-i via the ith upstream circulator 110-i. DLi The optical signal is input to the i-th O / E converter 112-i, and the wavelength is λ DLi The optical signal that is not the i-th downstream circulator 119-i is input to the (i+1)-th base station 11-(i+1) via the i-th downstream circulator 119-i. Furthermore, the optical signal received by the ith base station 11-i from the downstream side is input to the ith multiplexing unit 118-i via the ith downstream circulator 119-i. Thereafter, the optical signal input from the ith downstream circulator 119-i and the optical signal input from the ith E / O converter 117-i are multiplexed in the ith multiplexing unit 118-i, and the multiplexed signal is input to the upstream device via the ith upstream circulator 110-i.

[0050] The optical communication system 1 in the second embodiment can reduce the number of transmission paths connecting devices compared to the optical communication system 1 in the first embodiment.

[0051] Other Embodiments One embodiment of the present invention has been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0052] In the optical communication system 1 according to the first embodiment, the two transmission lines connecting the devices are, for example, two fibers, but may be two cores of a multi-core fiber.

[0053] In the optical communication system 1 according to the above-described embodiment, the string of cascaded base stations 11 does not branch off midway, but in other embodiments, the string of base stations 11 may branch off midway. In other words, two or more base stations 11 may be connected downstream of a certain base station 11.

[0054] In the above embodiment, the multiplexing unit 102, the demultiplexing unit 103, the multiplexing unit 106, the demultiplexing unit 111, and the multiplexing unit 118 transmit multiple optical signals with different wavelengths by demultiplexing or multiplexing optical signals based on wavelength, but this is not limited to this. For example, the optical communication system 1 may multiplex and transmit optical signals by frequency division multiplexing or time division multiplexing.

[0055] The base station 11 may include a control unit 120. When the demultiplexing unit 111 and the multiplexing unit 118 multiplex optical signals by time division multiplexing, the circulator 114 may be a TDD switch, and the control unit 120 may control the TDD switch to switch between the connection between the transmitting amplifier 113 and the circulator 114 and the connection between the circulator 114 and the receiving amplifier 116. When the demultiplexing unit 111 and the multiplexing unit 118 multiplex optical signals by time division multiplexing, the wavelength λ of the optical signal transmitted by the i-th E / O conversion unit 101-i may be 1 / 2. DLi and the wavelength λ of the optical signal received by the i-th O / E conversion unit 104-i. ULi may be the same wavelength, e.g., λ DL1 and λ UL1 may be at the same wavelength.

[0056] The antenna 115 is an array antenna with a controllable beam direction, and the control unit 120 may control the antenna 115 to change the beam direction in which the antenna 115 transmits and receives signals.

[0057] The control unit 120 may be controlled based on a control signal received from the central station 10. The control signal may be subcarrier-multiplexed, polarization-multiplexed, or wavelength-multiplexed onto a downstream optical signal transmitted by the central station 10, and then transmitted to the base station 11. The wavelength of the control signal is λ DLi and λ DLi The wavelength may be different from either of the wavelengths.

[0058] The optical communication system 1 employs, but is not limited to, an analog RoF. The optical communication system 1 may employ a digital RoF (for example, CPRI or eCPRI) or digital coherent transmission, in which the central station 10 includes an A / D converter, each base station 11 includes a D / A converter, and the central station 10 transmits a digital signal.

[0059] The present invention can be applied even when the central station 10 and the base station are connected by a mobile fronthaul in the optical communication system 1. [Explanation of symbols]

[0060] 10 aggregation station, 11 base station, 12 downstream transmission path, 13 upstream transmission path, 14 transmission path, 100 transmitting unit, 101 E / O conversion unit, 102 multiplexing unit, 103 branching unit, 104 O / E conversion unit, 105 receiving unit, 106 multiplexing unit, 110 upstream circulator, 111 branching unit, 112 O / E conversion unit, 113 transmitting amplifier, 114 circulator, 115 antenna, 116 receiving amplifier, 117 E / O conversion unit, 118 multiplexing unit, 119 downstream circulator

Claims

1. An optical communication system including a central station and a plurality of base stations, the plurality of base stations being connected in series with the central station at the head, The plurality of base stations include: a demultiplexing unit that demultiplexes a received signal into a first demultiplexed signal having a wavelength assigned to the station and a second demultiplexed signal having another wavelength; a multiplexing unit that multiplexes a signal received from a downstream device and a signal processed in the local station; an upstream circulator that transmits a signal received from an upstream device to the demultiplexing unit and transmits the combined signal received from the multiplexing unit to an upstream device; a downstream circulator that transmits the second demultiplexed signal received from the demultiplexing unit to a downstream device and transmits a signal received from the downstream device to the multiplexing unit; Equipped with Optical communication system.

2. The said station A signal received from the downstream device and a signal processed by the local station are combined and transmitted to the upstream device via the transmission path along which the signal received from the upstream device was transmitted. transmitting the second demultiplexed signal to the downstream device via a transmission path through which the signal received from the downstream device has been transmitted; 2. The optical communication system according to claim 1.

3. A base station in an optical communication system in which a central station and a plurality of base stations are connected in series with the central station at the head, a demultiplexing unit that demultiplexes a received signal into a first demultiplexed signal having a wavelength assigned to the station and a second demultiplexed signal having another wavelength; a multiplexing unit that multiplexes a signal received from a downstream device and a signal processed in the local station; an upstream circulator that transmits a signal received from an upstream device to the demultiplexing unit and transmits the combined signal received from the multiplexing unit to an upstream device; a downstream circulator that transmits the second demultiplexed signal received from the demultiplexing unit to a downstream device and transmits a signal received from the downstream device to the multiplexing unit; A post office equipped with:

4. A communication method for a base station in an optical communication system in which a central station and a plurality of base stations are connected in series with the central station at the head, the method comprising: a demultiplexing unit demultiplexing the received signal into a first demultiplexed signal having a wavelength assigned to the local station and a second demultiplexed signal having another wavelength; a multiplexing unit multiplexing a signal received from a downstream device and a signal processed in the local station; an upstream circulator provided between the demultiplexing unit and the multiplexing unit, transmitting a signal received from an upstream device to the demultiplexing unit, and transmitting the multiplexed signal received from the multiplexing unit to the upstream device; a downstream circulator provided between the demultiplexing unit and the multiplexing unit, transmitting the second demultiplexed signal received from the demultiplexing unit to a downstream device, and transmitting a signal received from the downstream device to the multiplexing unit; A communication method for a base station having the above-mentioned features.

Images