Embodiments of this disclosure provide an apparatus and method for generating a transmitting sequence, a training sequence synchronization apparatus and method, an apparatus and method for estimating channel spacing and a system. The training sequence synchronization apparatus includes: a delay correlation processing unit configured to parallelly perform autocorrelation operations of different delay amounts on a receiving sequence containing a periodic training sequence to obtain multiple parallel correlation sequences; a superimposition processing unit configured to perform a superimposition operation on the multiple parallel correlation sequences to obtain a synchronization correlation sequence; and a synchronization extracting unit configured to perform a synchronization position extraction on the synchronization correlation sequence to obtain a synchronization position of the training sequence. With the embodiments of this disclosure, anti-noise performance of the training sequence may be enhanced.

Techniques are described for determining, with a first optical node, a correction factor indicative of an amount of optical power loss that a Raman amplifier in a second optical node causes in an optical signal having a first wavelength that is transmitted by the first optical node and received by the second optical node, transmitting, with the first optical node to the second optical node, information, based on the determined correction factor, that is to be used for determining a gain of the Raman amplifier, and transmitting, with the first optical node to the second optical node, an optical signal having a second wavelength that is to be amplified by the Raman amplifier.

A wavelength demultiplexer includes a photonic circuit and a control circuit that adjusts wavelength characteristics of the photonic circuit. The photonic circuit converts two orthogonal polarized waves contained in the incident light into two same polarized waves, which are supplied to a first optical demultiplexing circuit and a second optical demultiplexing circuit provided in the photonic circuit and having the same configuration. The photonic circuit supplies a total output power of monitor lights extracted from the same positions in the first optical demultiplexing circuit and the second optical demultiplexing circuit to the control circuit. The control circuit controls a first wavelength characteristic of the first optical demultiplexing circuit and a second wavelength characteristic of the second optical demultiplexing circuit based on the total output power of the monitor lights.

A wavelength demultiplexer includes a photonic circuit and a control circuit that adjusts wavelength characteristics of the photonic circuit. The photonic circuit converts two orthogonal polarized waves contained in the incident light into two same polarized waves, which are supplied to a first optical demultiplexing circuit and a second optical demultiplexing circuit provided in the photonic circuit and having the same configuration. The photonic circuit supplies a total output power of monitor lights extracted from the same positions in the first optical demultiplexing circuit and the second optical demultiplexing circuit to the control circuit. The control circuit controls a first wavelength characteristic of the first optical demultiplexing circuit and a second wavelength characteristic of the second optical demultiplexing circuit based on the total output power of the monitor lights.

An optical line device for use in an optical line system is configured to connect to a second optical line device via a transmit fiber and a receive fiber. The optical line device includes a transmitter connected to the transmit fiber via an output port of the optical line device, wherein the transmitter is configured to transmit a polarization probe signal at a wavelength outside of a band of wavelengths used for traffic-bearing channels in the optical line signal, to a second polarimeter receiver at the second optical line device; and a polarimeter receiver connected to the receive fiber via an input port of the optical line device, wherein the polarimeter receiver is configured to receive a second polarization probe signal from a second transmitter transmitted from the second optical line device and to derive a measurement of SOP on the receive fiber based on the second polarization probe signal.

An optical fibre assembly comprises a hollow core optical waveguide comprising a hollow core surrounded by a structured arrangement of longitudinally extending capillaries providing an inner cladding surrounded by an outer cladding; a diagnostic solid core optical waveguide comprising a solid core surrounded by a cladding, and extending substantially parallel to the hollow core optical waveguide; and a jacket surrounding both the hollow core optical waveguide and the solid core optical waveguide and forming a common mechanical environment for the hollow core optical waveguide and the solid core optical waveguide. The optical fibre assembly may be or may comprise or be included in an optical fibre cable, and may be used in a method for testing hollow core optical waveguides.

A composite connector for optical power meter is provided, which includes a fixation base and an active connection base. The fixation base is installed on an optical power meter; the fixation base includes a left hole, a right hole and a central hole. The active connection base includes a bottom plate, an active pin, a first fiber socket and a second fiber socket. The first fiber socket and the second fiber socket are disposed on the bottom plate. The active pin penetrates through the bottom plate and is inserted into the left hole, whereby a first circle, whose center is at the active pin and circumference passes through the first fiber socket as well as the second fiber socket, overlaps a second circle, whose center is at the left hole and circumference passes through the central hole, in the normal direction of the active connection base.

Embodiments of techniques for inverse design of physical devices are described herein, in the context of generating designs for photonic integrated circuits (including a multi-channel photonic demultiplexer). In some embodiments, an initial design of the physical device is received, and a plurality of sets of operating conditions for fabrication of the physical device are determined. In some embodiments, the performance of the physical device as fabricated under the sets of operating conditions is simulated, and a total performance loss value is backpropagated to determine a gradient to be used to update the initial design. In some embodiments, instead of simulating fabrication of the physical device under the sets of operating conditions, a robustness loss is determined and combined with the performance loss to determine the gradient.

Embodiments of techniques for inverse design of physical devices are described herein, in the context of generating designs for photonic integrated circuits (including a multi-channel photonic demultiplexer). In some embodiments, an initial design of the physical device is received, and a plurality of sets of operating conditions for fabrication of the physical device are determined. In some embodiments, the performance of the physical device as fabricated under the sets of operating conditions is simulated, and a total performance loss value is backpropagated to determine a gradient to be used to update the initial design. In some embodiments, instead of simulating fabrication of the physical device under the sets of operating conditions, a robustness loss is determined and combined with the performance loss to determine the gradient.

A breakdown determination system includes a switching device that switches a transmission path of optical signals between an upper network and a lower network, one or more intermediate communication devices that relay communication between the upper network and the lower network, a selection device that selects a standby port of the intermediate communication devices, a measurement device that connects to the selected standby port via the switching device and measures an optical signal of the connected standby port, a determination device that determines whether an intermediate communication device including the selected standby port breaks down based on a result of measuring the optical signal, and a storage device that stores a result of determining whether the intermediate communication device breaks down.