[Problem] To determine a time difference between clocks which, for example, are placed far apart from each other with high accuracy at low cost. [Solution] In a time comparison system 20, an intermediate station 21 disperses a single optical signal 21c in the spatial region using the optical complex amplitude modulation to simultaneously transmit the optical signal 21c to a plurality of comparative stations 22 and 23 apart from each other. The intermediate station 21 transmits the optical signal 21c while changing the transmission angle using phase modulation, performs intensity scanning for the reflected light c1 of the optical signal 21c, and detects the peak intensity to determine the directions of the comparative stations 22 and 23. The reflected light c1 of the optical signal 21c transmitted to the comparative stations 22 and 23 of which the direction have been determined, is detected to determine a round-trip propagation delay time between the intermediate station 21 and each of the comparative stations 22 and 23. The difference calculation unit 25 calculates a sum of time difference between each of times to and tb associated with the comparative stations 22 and 23 and the time tc associated with the intermediate station 21, and the determined propagation delay time to determine time information of each of the comparative stations 22 and 23. Based on the result of subtracting, from the time information of the comparative stations 22, the time information of the comparative stations 23, the time difference between the comparative stations 22 and 23 is determined.

Systems and methods are provided for enhancing techniques for provisioning optical channels to allow optical networks to operate in an optimal fashion. A method, according to one implementation, includes utilizing a plurality of modems to measure optical performance parameters of a plurality of optical channels of an optical spectrum. Each optical channel is previously unassigned in an unknown optical link system to be commissioned. The modems are arranged within a group for communicating optical signals within the optical spectrum across the unknown optical link system to an unknown far-end network element. The method also includes provisioning the plurality of optical channels based on the measured optical performance parameters to enable data communication between the near-end network element and the far-end network element. Before commissioning, the unknown optical link system does not allow data communication between the near-end network element and the far-end network element.

Chromatic dispersion compensation is performed in one or more pluggable optical transceiver (POT) devices operating within an intensity-modulated direct-detection (IMDD) optical network. Compensation is performed within each POT using an electrical and/or optical chromatic dispersion module which are controlled by a set of parameters. A network computing device includes a computer processor and a host management interface for communicating with the POT. In the event of a link failure, the computer processor determines a second set of parameters to control the one or more dispersion compensation module(s) of the POT. The second set of parameters are different from a first set of parameters used to control the one or more compensation module(s) in the case of a first optical path. The computer processor causes the POT to use the second set of parameters in place of the first set of parameters.

A method and system are provided for continuously monitoring bandwidth utilization in real time on a backbone of a network. Prefixes using the highest traffic can be identified and additional bandwidth can be provisioned in the form of optical transponder wavelengths. The additional bandwidth can be an express path that passes directly through optical nodes (thereby bypassing transit network devices) to the destination optical node. A centralized controller can perform the monitoring of the network devices, decide that an express path needs to be generated, and control both the network device and the optical network nodes to generate the express path from the network device, through the optical network, to the destination network device. The controller can apply and remove IP static routes and IP addresses associated with an express path. Additionally, the controller can request the setup or tear-down of an optical wavelength within the optical network.

The present invention discloses a capacity optimization method for a mobile optical wireless communication system and a communication method and system. The capacity optimization method includes the following steps: establishing a mobile channel impulse response model; calculating an electrical signal-to-noise ratio (SNR) of an output of a receiver; calculating bit error rate (BER) values of an optical wireless communication system in different candidate modulation formats according to the electrical SNR of the output of the receiver; selecting a first modulation format and a second modulation format from the different candidate modulation formats; determining quantities of chips in the first modulation format and the second modulation format in each data frame; and building a time domain hybrid modulation frame according to the quantities of chips in the first modulation format and the second modulation format, modulating data by using the time domain hybrid modulation frame, and performing data transmission.

An optronic transceiver module is disclosed. The optronic transceiver module includes an m to n main optical coupler capable of splitting a downlink signal into n downlink optical signals of the same power to be transmitted in n optical fibres, a first uplink optical coupler capable of splitting an uplink signal into two optical signals split according to a predetermined reference power ratio and delivering a low-power signal and a high-power signal, a first power measurement photodiode delivering a power measurement associated with a first low-power signal, the main optical coupler being capable of aggregating the high-power optical signal and a second uplink optical signal representative of an optical signal received via a second optical fibre, into an aggregated uplink optical signal.

An optronic transceiver module capable of implementing an optical bidirectional communication of the point to point type via at least one main optical fibre is disclosed. The optronic transceiver module includes a first optical module for supervising an uplink signal received via the main optical fibre delivering a first supervision result, a first optical module for switching the bidirectional communication via the main optical fibre to a bidirectional communication via a backup optical fibre, and vice versa, the first optical switching module being controlled by the first optical supervision module depending on the first supervision result delivered.

An optical demultiplexer includes a first optical-processing-circuit to include first to third AMZs, each including a pair-of-arms of different lengths, the first AMZ outputting, to the second AMZ, a first signal-light-component and a first local-oscillation-light with center wavelengths adjacent to each other among a plurality of signal-light-components and a plurality of local-oscillation-lights inputted to the pair-of-arms, and outputting, to the third AMZ, a second signal-light-component with a same center wavelength as the first local-oscillation-light and a second local-oscillation-light with the same center wavelength as the first signal-light-component, the second AMZ outputting the first signal-light-component and the first local-oscillation-light, which are inputted to the pair-of-arms from the first AMZ, to a second optical-processing-circuit and a third optical-processing-circuit, respectively, and the third AMZ outputting the second local-oscillation-light and the second signal-light-component, which are inputted to the pair-of-arms from the first AMZ, to the second optical-processing-circuit and the third optical-processing-circuit, respectively.

A skew compensation system for a coherent optical communication network includes a transmitter modulator having a first driver input for receiving a first signal from a first channel, a second driver input for receiving a second signal from a second channel, a source input for receiving a continuous wave source signal, and a modulation output in communication with an optical transport medium of the network. The system further includes a tunable delay line disposed between the second channel and the second driver input for inserting a pre-determined training sequence onto the second signal prior to the second driver input, and a processor for determining a skew amount between the second signal at the second driver input and the first signal at the first driver input, calculating a pre-compensation value corresponding to the skew amount, and reducing the skew amount at the modulation output according to the pre-compensation value.

The disclosed systems and methods for optical filter fault localization. The optical filter fault localization is based on: i) determining an accumulated noise density at frequencies where ASE noise is filtered out by a faulty optical filter in an optical signal; ii) comparing the accumulated noise density with predicted accumulated noise densities, the predicted accumulated noise densities representing noises predicted from a plurality of optical filters to a receiver; and iii) determining, based on the comparison of the accumulated noise density and the predicted accumulated noise densities, a location of the faulty optical filter.