Abstract: An optical amplifier includes a pump light source, a coupler, a gain medium, and a gain flattening filter. A gain curve of the optical amplifier is symmetric relative to a target gain curve. Distortion states of any two symmetric gain curves are opposite. The pump light source is configured to provide pump light. The coupler is configured to couple the pump light to the gain medium. The gain medium is configured to amplify, based on the pump light, signal light input to the optical amplifier. The gain flattening filter is configured to filter the amplified signal light, and output the filtered signal light.

Abstract: The technology of this application relates to a fault detection method for an optical switching apparatus, a network device, and a system, to improve accuracy and efficiency of detecting whether the optical switching apparatus is faulty. The method includes sending a probe optical signal to a target path, where the probe optical signal is to be transmitted along the target path, and the target path includes at least one optical switching apparatus, receiving a plurality of reflected optical signals from the target path, where the plurality of reflected optical signals are formed after the probe optical signal is reflected by the target path, determining a target reflected optical signal in the plurality of reflected optical signals, where the target reflected optical signal is a reflected optical signal reflected by the optical switching apparatus, and determining, based on the target reflected optical signal, whether the optical switching apparatus is faulty.

Abstract: Example fiber amplifiers and gain adjustment methods for the fiber amplifiers are described. One example fiber amplifier includes a first power amplifier, a wavelength level adjuster, and a controller, where the first power amplifier is connected to the wavelength level adjuster. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal, and the control output end is configured to output a first amplification control signal to the first power amplifier, and output an adjustment control signal to the wavelength level adjuster. The wavelength level adjuster is configured to perform power adjustment on each wavelength in a separate manner based on the adjustment control signal.

Abstract: Example fiber amplifiers and gain adjustment methods for the fiber amplifiers are described. One example fiber amplifier includes a first power amplifier, a wavelength level adjuster, and a controller, where the first power amplifier is connected to the wavelength level adjuster. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal, and the control output end is configured to output a first amplification control signal to the first power amplifier, and output an adjustment control signal to the wavelength level adjuster. The wavelength level adjuster is configured to perform power adjustment on each wavelength in a separate manner based on the adjustment control signal.

Abstract: Example fiber amplifiers and gain adjustment methods for the fiber amplifiers are described. One example fiber amplifier includes a first power amplifier, a wavelength level adjuster, and a controller, where the first power amplifier and the wavelength level adjuster are sequentially connected. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal of the fiber amplifier, and the control output end is configured to output a first amplification control signal to the first power amplifier, and output an adjustment control signal to the wavelength level adjuster. The wavelength level adjuster is configured to perform power adjustment on each wavelength based on the adjustment control signal.

Abstract: Example fiber amplifiers and gain adjustment methods for the fiber amplifiers are described. One example fiber amplifier includes a first power amplifier, a wavelength level adjuster, and a controller, where the first power amplifier and the wavelength level adjuster are sequentially connected. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal of the fiber amplifier, and the control output end is configured to output a first amplification control signal to the first power amplifier, and output an adjustment control signal to the wavelength level adjuster. The wavelength level adjuster is configured to perform power adjustment on each wavelength based on the adjustment control signal.

Abstract: An upgrading method, a system, and an apparatus of a low-density wavelength division multiplexing (WDM) system are provided. The method includes: detecting an output wavelength shift of a wavelength conversion unit, and adjusting an output wavelength of the wavelength conversion unit having the output wavelength shift higher than a threshold, so that the output wavelength shift of the wavelength conversion unit is lower than the threshold; adjusting an adjustable interleaved demultiplexer, until requirements for a demultiplexing parameter of a high-density WDM system are met. Thus, the problem that services are interrupted when a low-density MDM system is upgraded to a high-density MDM system is solved. A WDM system, and a wavelength multiplexing/demultiplexing apparatus and method are also provided.

Abstract: An upgrading method, a system, and an apparatus of a low-density wavelength division multiplexing (WDM) system are provided. The method includes: detecting an output wavelength shift of a wavelength conversion unit, and adjusting an output wavelength of the wavelength conversion unit having the output wavelength shift higher than a threshold, so that the output wavelength shift of the wavelength conversion unit is lower than the threshold; adjusting an adjustable interleaved demultiplexer, until requirements for a demultiplexing parameter of a high-density WDM system are met. Thus, the problem that services are interrupted when a low-density MDM system is upgraded to a high-density MDM system is solved. A WDM system, and a wavelength multiplexing/demultiplexing apparatus and method are also provided.