The Bi-Di coherent transmission system is configured with at least one pair of modules coupled to one another via a single fiber. The modules each are configured with a pair of laser outputting two reference signals at respective different wavelengths λ.sub.1o and λ.sub.2o, photonic transceiver and a wavelength division multiplexer (WDM) coupler. The photonic transceivers each have transmitter and receiver branches integrated in a photonic circuit and receiving the reference signals. The transmitter is configured to modulate the received reference signals λ.sub.1oT and λ.sub.2oT which are further coupled into the WDM coupler. The WDM couplers each sort out one of the modulated signals and transmit the other modulated signal such that the transmitted modulated signal at different wavelengths λ.sub.1oT and λ.sub.2oT are coupled into respective opposite ends of the fiber and propagate towards one another in opposite directions. The transmitted modulated signals arc coupled into respective branches through the WDM couplers with each transmitted modulated signal interfering with the reference signals at wavelengths λ.sub.1oT and λ.sub.2oT. The photodiodes of respective receiving brandies are configured to detect a beat frequency of the interfering signals at the same wavelength.

A wavelength selective switch includes an optical fiber array, a multiplexing/demultiplexing component, and a transmission direction adjustment component. The optical fiber array includes a first optical fiber and at least one second optical fiber. The first offset is used to compensate for a second offset of a diffraction spectrum generated when a plurality of single-wavelength optical signals obtained after an optical input signal is processed by the multiplexing/demultiplexing component arrive at the transmission direction adjustment component, so that the second offset of the diffraction spectrum of the plurality of single-wavelength optical signals arriving at the transmission direction adjustment component is 0 or may be ignored. An optical system has a simple structure, and no optical element needs to be added. This increases optical design freedom, facilitates optical path system commissioning, and reduces reliability risks and costs of subsequent products.

This application provides a spectrum resource configuration method, a network device, and a system. The method includes: A network device determines spectrum resources to be used by a to-be-opened channel, where the spectrum resources to be used by the to-be-opened channel include first spectrum resources and a second spectrum resource, the first spectrum resources are original spectrum resources of the to-be-opened channel, the second spectrum resource is some of original spectrum resources of an adjacent channel of the to-be-opened channel, and the original spectrum resources of the adjacent channel are adjacent to the original spectrum resources of the to-be-opened channel; and opens the to-be-opened channel based on the spectrum resources to be used by the to-be-opened channel.

A radio over fiber (RoF) system and a nonlinear compensation method, where the RoF system includes a BBU and an RRU, the RRU includes an electrical component, and the BBU includes a downlink and a feedback link. A predistortion module and an optical component are disposed on the downlink, an input end of the feedback link is connected to an output end of the optical component, and the feedback link is configured to feed back, to the predistortion module, a nonlinear signal output by the optical component. The RoF system further includes a temperature detection module configured to detect a temperature value of the electrical component, and transmit the temperature value to the predistortion module. The predistortion module is configured to perform digital predistortion DPD on a baseband signal based on the temperature value and the nonlinear signal.

A dummy optical signal generation apparatus includes a multi-longitudinal mode laser configured to provide a light source signal. The dummy optical signal generation also includes a comb optical bandpass filter. The light source signal provided by the multi-longitudinal mode laser outputs a dummy optical signal through the comb optical bandpass filter. The dummy optical signal is an optical signal that does not comprise service information.

An optical module is disclosed. The optical module includes a first downlink port, a second downlink port, a directional coupler, a optical attenuator, a first photodiode (PD), and a second PD. The directional coupler, connected to the first downlink port, is configured to receive a downlink optical signal. The second PD connected to the directional coupler, is configured to obtain a power value. If the power value is greater than a first threshold, the optical attenuator is configured to receive a attenuation control signal, and attenuate, based on the attenuation control signal, a power of an optical signal passing through the second downlink port. The first PD is configured to: convert the downlink optical signal into a downlink electrical signal, and convert the optical signal passing through the second downlink port into an electrical signal. Both the first downlink port and the second downlink port are connected to the first PD.

A link group configuration method includes obtaining first status information of M links between a source end device and a receive end device, where the first status information indicates a status of a differential delay between any two of the M links, obtaining first capability information of the receive end device, where the first capability information indicates a first capability of performing differential delay compensation on the M links by the receive end device, grouping N of the M links into a first link group based on the first status information and the first capability information, and sending first configuration information to a second device, where the first configuration information includes information used to indicate the first link group.

A wavelength division multiplexing filter comprises: a first multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers, and a second multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers; wherein the first multi-order Mach-Zehnder interferometer and the second multi-order Mach-Zehnder interferometer are included in a group of multiple multi-order Mach-Zehnder interferometers arranged within a binary tree arrangement, the binary tree arrangement comprising: a first set of a plurality of multi-order Mach-Zehnder interferometers, the first set including the first multi-order Mach-Zehnder interferometer, and having an associated spectral response with a first spacing between adjacent passbands, and a second set of at least twice as many multi-order Mach-Zehnder interferometers as in the first set, the second set including the second multi-order Mach-Zehnder interferometer, and having an associated spectral response with a second spacing between adjacent passbands that is twice the first spacing.

A wavelength division multiplexing filter comprises: a first multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers, and a second multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers; wherein the first multi-order Mach-Zehnder interferometer and the second multi-order Mach-Zehnder interferometer are included in a group of multiple multi-order Mach-Zehnder interferometers arranged within a binary tree arrangement, the binary tree arrangement comprising: a first set of a plurality of multi-order Mach-Zehnder interferometers, the first set including the first multi-order Mach-Zehnder interferometer, and having an associated spectral response with a first spacing between adjacent passbands, and a second set of at least twice as many multi-order Mach-Zehnder interferometers as in the first set, the second set including the second multi-order Mach-Zehnder interferometer, and having an associated spectral response with a second spacing between adjacent passbands that is twice the first spacing.

An optical wavelength multiplexing transmission device includes: a demultiplexer configured to demultiplex a wavelength multiplexing signal for each wavelength band from a multiplexed signal that includes wavelength multiplexing signals in a plurality of the wavelength bands; a processor configured to detect an optical power value of each wavelength multiplexing signal for each wavelength band; calculate a compensation amount used to compensate a tilt of the wavelength multiplexing signal, by using the optical power value and a predetermined calculation expression; and compensate the tilt of the wavelength multiplexing signal, based on the compensation amount; and a multiplexer configured to multiplex each wavelength multiplexing signal compensated by the processor and output the wavelength multiplexing signal to a transmission line.