The present disclosure aims to enable communication to be performed with stable quality even when a user uses a terminal while moving. In the wireless communication system according to the present disclose, a switching control unit 15 sets switching illuminance p.sub.th for maintaining illuminance of an optical signal received by a terminal 91 at requested illuminance corresponding to throughput or higher during the time until connection switching between the communication with an optical wireless access point 92 and the communication with an RF wireless access point 93 is completed, and when the received illuminance p becomes lower than the switching illuminance p.sub.th during connection with the optical wireless access point 92, the switching control unit 15 performs connection switching from the optical wireless communication to the RF wireless communication.

A long-distance high-precision optical fiber interference sensing and positioning system includes a sensing light path, a control terminal, a light source module, a front-end optical processing module, a back-end optical processing module, a photoelectric conversion module, a digital signal collection module and a MCU central processing module. The control terminal is provided with a signal processing and positioning device for calculating and positioning sensing signal positioning information. The present system can solve the security problem of an ultra-long-distance optical cable, can send alarm information in a timely manner with regard to an intrusion event by means of vibration positioning, and can also solve the problem of occupation of an optical cable channel, and improves the utilization efficiency of the optical cable by means of wavelength division multiplexing technology.

An object of the present invention is to provide an optical transmission system capable of controlling a transmission capacity and a signal processing load of a MIMO equalizer, without depending on the number of propagation modes of the optical fiber. The present optical transmission system includes an optical fiber 11 with the number of spatial modes being L (an integer of 2 or greater), an optical multiplexer 13 connected to one end of the optical fiber 11 and configured to input M (a natural number of L or less) signal beams of light to the optical fiber 11 and cause the M input signal beams of light to be propagated for each of the spatial modes of the optical fiber 11, an optical demultiplexer 14 connected to another end of the optical fiber 11 and configured to demultiplex a propagated beam of light propagated through the optical fiber 11 for each of the spatial modes of the optical fiber 11, N (N=L) receivers 15 configured to each receive a demultiplexed beam of light obtained by demultiplexing the propagated beam of light, a signal generation apparatus 17 configured to generate P (an integer of from M to L) combined signals from the N received signals, and a P×M MIMO equalizer 16 configured to receive the P combined signals to output M demodulated signals.

A method may include obtaining a topology of an optical network. The topology may indicate multiple optical links within the optical network. The method may also include obtaining a routing metric for each of the optical links. The routing metric may be used in selecting routes through the optical network along the multiple optical links. The method may further include obtaining a signal noise tolerance of an optical signal to be routed through the optical network and adjusting routing metrics of one or more of the multiple optical links based on the signal noise tolerance of the optical signal. The method may also include after the routing metrics of the one or more of the multiple optical links are adjusted, determining a route for the optical signal through the optical network along two or more of the multiple optical links based on the routing metrics of the multiple optical links.

A method may include obtaining a topology of an optical network. The topology may indicate multiple optical links within the optical network. The method may also include determining a signal noise tolerance for each of multiple optical signal types supported by the optical network and obtaining an optical noise for each of the multiple optical links. The method may also include determining a number of the multiple optical signal types that each of the multiple optical links is able to support based on the optical noise for each of the optical links and the signal noise tolerance for each of the multiple optical signal types and ranking the multiple optical links based on the number of the multiple optical signal types that each of the optical links is able to support.

An apparatus and method are disclosed with some embodiments including an analog and time to digital converter (ATDC) including a receiver, the receiver for receiving an analog channel input for conversion to a digital data, the digital data having at least one bit, and a defined absolute reference time stamp, the defined absolute reference time stamp representing an absolute reference time associated with conversion of the analog channel input to the digital data and an analog-to-digital converter, the converter converting the analog channel input to the digital data.

A tentative decision is made for symbols on the basis of a received signal and a decision threshold, and a tentative decision signal including a sequence of the symbols is output. A scale value indicating a rate of increase or reduction of the received signal or a threshold change rate indicating a degree of change in the decision threshold is updated so that an appearance frequency of each of symbols included in the tentative decision signal matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission which is shared between a transmitting side and a receiving side, and an SN ratio is calculated using the scale value or the threshold change rate when a degree of agreement between the appearance frequencies is within a predetermined permissible range. When the scale value is updated, a tentative decision is made for the symbols on the basis of the received signal increased or reduced by the updated scale value and the decision threshold, and when the threshold change rate is updated, the tentative decision for the symbols is made on the basis of the received signal and the decision threshold to which the updated threshold change rate is applied.

A tentative decision is made for symbols on the basis of a received signal and a decision threshold, and a tentative decision signal including a sequence of the symbols is output. A scale value indicating a rate of increase or reduction of the received signal or a threshold change rate indicating a degree of change in the decision threshold is updated so that an appearance frequency of each of symbols included in the tentative decision signal matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission which is shared between a transmitting side and a receiving side, and an SN ratio is calculated using the scale value or the threshold change rate when a degree of agreement between the appearance frequencies is within a predetermined permissible range. When the scale value is updated, a tentative decision is made for the symbols on the basis of the received signal increased or reduced by the updated scale value and the decision threshold, and when the threshold change rate is updated, the tentative decision for the symbols is made on the basis of the received signal and the decision threshold to which the updated threshold change rate is applied.

Provided are a communication device, a communication controlling method, and a non-transitory computer-readable medium storing a communication controlling program that each make it possible to grasp the condition of communication quality. A communication device (1) includes acquiring means (2) configured to acquire quality information concerning a burst error that has occurred in an optical communication line. The communication device (1) includes estimating means (3) configured to estimate a first index value based on the quality information acquired by the acquiring means (2), the first index value indicating a degree of influence of the burst error on communication quality in a first communication device.

An object is to estimate a location where a communication failure occurs while reducing a load on an apparatus included in an upper layer in an optical communication system. Terminal stations communicate via an optical transmission line constituting an optical network and include one or more transponders. Failure cause estimation apparatuses monitors states of the transponders provided in each of the terminal stations and estimates a failure probability for each location where an occurrence of a failure is suspected. A failure analysis apparatus estimates a location where there is a risk of failure occurrence and a failure probability at the location where there is the risk of failure occurrence based on failure cause estimation results of the failure cause estimation apparatuses provided in the terminal stations.