Abstract: Optical transmission system transmits WDM signal from first node to second node via optical fiber. The optical transmission system includes: first OCM that detects optical power of each wavelength channel of the WDM signal in the first node; second OCM that detects optical power of each wavelength channel of the WDM signal in the second node; first processor that calculates linear SNR of each wavelength channel based on the optical power of each wavelength channel detected by the second OCM; second processor that calculates non-linear SNR of each wavelength channel based on the optical power of each wavelength channel detected by the first OCM; third processor that calculates GSNR for each wavelength channel using the linear SNR and the non-linear SNR; and fourth processor that controls transmission power of each wavelength channel of the WDM signal based on the GSNR of each wavelength channel.

Abstract: A forward Raman amplifier includes a plurality of pumping light sources with different wavelengths and the forward Raman amplifier, according to a fiber type or a zero-dispersion wavelength of the fiber, changes the number of pumping light sources to be emitted, changes a power ratio between the plurality of pumping light sources with the different wavelengths or changes wavelength characteristics of a gain, according to a fiber type.

Abstract: An optical transmission system includes a first optical node, a second optical node, and an optical fiber provided between the first optical node and the second optical node. The optical transmission system further includes: a signal generator provided in the first optical node and configured to generate an optical signal including a plurality of wavelength channels and an empty channel; an optical transmission circuit provided in the first optical node and configured to output the optical signal to the optical fiber; an optical channel monitor provided in the second optical node and configured to measure reception power of each channel in the optical signal received through the optical fiber; and a processor configured to determine a type of the optical fiber based on the reception power of the empty channel, the reception power being measured by the optical channel monitor.

Abstract: A decoding method includes: receiving a plurality of subcarrier signals each including encoded data; acquiring a predetermined amount of data from each of the plurality of subcarrier signals; correcting errors in the plurality of subcarrier signals by performing decoding arithmetic processing on the respective predetermined amounts of data acquired from the plurality of subcarrier signals in a time-division manner; and causing the decoding arithmetic processing to be consecutively performed on each of the predetermined amounts of data a predetermined number of times.

Abstract: An optical transmission system includes a first optical node, a second optical node, and an optical fiber provided between the first optical node and the second optical node. The optical transmission system further includes: a signal generator provided in the first optical node and configured to generate an optical signal including a plurality of wavelength channels and an empty channel; an optical transmission circuit provided in the first optical node and configured to output the optical signal to the optical fiber; an optical channel monitor provided in the second optical node and configured to measure reception power of each channel in the optical signal received through the optical fiber; and a processor configured to determine a type of the optical fiber based on the reception power of the empty channel, the reception power being measured by the optical channel monitor.

Abstract: Optical transmission system transmits WDM signal from first node to second node via optical fiber. The optical transmission system includes: first OCM that detects optical power of each wavelength channel of the WDM signal in the first node; second OCM that detects optical power of each wavelength channel of the WDM signal in the second node; first processor that calculates linear SNR of each wavelength channel based on the optical power of each wavelength channel detected by the second OCM; second processor that calculates non-linear SNR of each wavelength channel based on the optical power of each wavelength channel detected by the first OCM; third processor that calculates GSNR for each wavelength channel using the linear SNR and the non-linear SNR; and fourth processor that controls transmission power of each wavelength channel of the WDM signal based on the GSNR of each wavelength channel.

Abstract: Optical transmission device is provided in one of a plurality of nodes in an optical network. Different carrier frequencies are respectively allocated to the plurality of nodes. The optical transmission device includes: transmitter, splitter and receiver. The transmitter generates a first subcarrier optical signal with a first subcarrier established on a low-frequency side of a first carrier frequency and a second subcarrier optical signal with a second subcarrier established on a high-frequency side of the first carrier frequency. The splitter splits an optical signal including the first subcarrier optical signal and the second subcarrier optical signal. The output of the splitter is guided to first and second adjacent nodes. The receiver recovers data carried by the first subcarrier and data carried by the second subcarrier from received optical signal. A difference between carrier frequencies of adjacent nodes corresponds to a bandwidth of the subcarrier.

Abstract: Optical transmission device is provided in one of a plurality of nodes in an optical network. Different carrier frequencies are respectively allocated to the plurality of nodes. The optical transmission device includes: transmitter, splitter and receiver. The transmitter generates a first subcarrier optical signal with a first subcarrier established on a low-frequency side of a first carrier frequency and a second subcarrier optical signal with a second subcarrier established on a high-frequency side of the first carrier frequency. The splitter splits an optical signal including the first subcarrier optical signal and the second subcarrier optical signal. The output of the splitter is guided to first and second adjacent nodes. The receiver recovers data carried by the first subcarrier and data carried by the second subcarrier from received optical signal. A difference between carrier frequencies of adjacent nodes corresponds to a bandwidth of the subcarrier.

Abstract: A decoding method includes: receiving a plurality of subcarrier signals each including encoded data; acquiring a predetermined amount of data from each of the plurality of subcarrier signals; correcting errors in the plurality of subcarrier signals by performing decoding arithmetic processing on the respective predetermined amounts of data acquired from the plurality of subcarrier signals in a time-division manner; and causing the decoding arithmetic processing to be consecutively performed on each of the predetermined amounts of data a predetermined number of times.

Abstract: An optical branching and insertion device includes an optical splitter that branches an input optical signal, and outputs the branched optical signal from a first output port and a second output port; a wavelength selective switch that allows passage of an optical signal of a predetermined wavelength from among optical signals input to a first input port from the first output port, and outputs the optical signal of the predetermined wavelength and an optical signal inputted from a second input port; and a processor that executes a process to expand a band through which the optical signal of the predetermined wavelength is allowed to pass, the process being executed when a channel allocated to a wavelength of the optical signal inputted from the second input port and a channel allocated to the predetermined wavelength are not adjacent.

Abstract: A communication system including: a transmission apparatus configured to modulate a first light by using a first signal to be transferred and a second signal having a frequency different from a frequency of the first signal so as to generate a first optical signal, modulate a second light by using a third signal to be transferred and a fourth signal having a frequency different from a frequency of the third signal so as to generate a second optical signal, polarization-multiplex the first optical signal and the second optical signal, and transmit a polarization-multiplexed optical signal in which the first optical signal and the second optical signal are polarization-multiplexed, each of the first light and the second light being polarized; and a measuring apparatus configured to measure powers of the second signal and the fourth signal which are included in the polarization-multiplexed optical signal transmitted from the transmission apparatus.

Abstract: An optical adding and dropping device includes a drop section including an input port and having a through port and a plurality of drop ports set as output ports, a first multiplexer adapted to multiplex light from the through port and light from a plurality of add ports, and a spectrum foot removing section provided on the input side of the first multiplexer and adapted to remove a foot of a spectrum of light to be inputted from the add ports to the first multiplexer. The optical adding and dropping device can be configured at a low cost while it has adding and dropping functions.

Abstract: An optical branching and insertion device includes an optical splitter that branches an input optical signal, and outputs the branched optical signal from a first output port and a second output port; a wavelength selective switch that allows passage of an optical signal of a predetermined wavelength from among optical signals input to a first input port from the first output port, and outputs the optical signal of the predetermined wavelength and an optical signal inputted from a second input port; and a processor that executes a process to expand a band through which the optical signal of the predetermined wavelength is allowed to pass, the process being executed when a channel allocated to a wavelength of the optical signal inputted from the second input port and a channel allocated to the predetermined wavelength are not adjacent.

Abstract: Where add optical signals have k different bit rates, an add controller is connected to k (<N) of N input ports and sends the add optical signals to the k input ports to perform add control. A drop controller is connected to m (<M) of M output ports and performs drop control on optical signals from the m output ports. The k input ports of an N×M wavelength selective switch and the add controller are connected by k links (L1 to Lk) which have introduced therein dispersion compensators for compensating chromatic dispersions of the add optical signals with the respective bit rates. The add controller selects a link through which an add optical signal is to be passed for dispersion compensation, and sends the signal to the N×M wavelength selective switch via the selected link.

Abstract: Where add optical signals have k different bit rates, an add controller is connected to k (<N) of N input ports and sends the add optical signals to the k input ports to perform add control. A drop controller is connected to m (<M) of M output ports and performs drop control on optical signals from the m output ports. The k input ports of an N×M wavelength selective switch and the add controller are connected by k links (L1 to Lk) which have introduced therein dispersion compensators for compensating chromatic dispersions of the add optical signals with the respective bit rates. The add controller selects a link through which an add optical signal is to be passed for dispersion compensation, and sends the signal to the N×M wavelength selective switch via the selected link.

Abstract: A communication system including: a transmission apparatus configured to modulate a first light by using a first signal to be transferred and a second signal having a frequency different from a frequency of the first signal so as to generate a first optical signal, modulate a second light by using a third signal to be transferred and a fourth signal having a frequency different from a frequency of the third signal so as to generate a second optical signal, polarization-multiplex the first optical signal and the second optical signal, and transmit a polarization-multiplexed optical signal in which the first optical signal and the second optical signal are polarization-multiplexed, each of the first light and the second light being polarized; and a measuring apparatus configured to measure powers of the second signal and the fourth signal which are included in the polarization-multiplexed optical signal transmitted from the transmission apparatus.

Abstract: An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.

Abstract: In order to compensate for chromatic dispersion ad dispersion slope over an entire wavelength band of the optical signal, the wavelength band is split into a plurality of bands, and chromatic dispersion compensation is made to make chromatic dispersion in a central wavelength of each of the bands zero.

Abstract: An optimally-sized optical cross-connect that switches optical signal paths with a minimum number of wavelength selective switches and their interconnections. To switch optical signals of N routes (N=1, 2, . . . ), an optical cross-connect includes a 2×N (2-input, N-output) wavelength selective switch for each of N input routes and a N×2 (N-input, 2-output) wavelength selective switch for each of N output routes. One input port of each 2×N wavelength selective switch receives an optical signal from a corresponding input route, while the other input port of the same receives an optical add signal from a corresponding add route. One output port of each N×2 wavelength selective switch outputs an optical signal to a corresponding output route, while the other output port outputs an optical drop signal to a corresponding drop route.

Abstract: An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.