The present disclosure provides a method and a device for controlling a downlink optical signal in a passive optical network, and a computer-readable storage medium. The method includes: monitoring power of a downlink optical signal in a process of receiving the downlink optical signal; and adjusting an attenuation value of a variable optical attenuator at an ONU side according to the power of the downlink optical signal until the power of the downlink optical signal falls within a preset power range. The variable optical attenuator at the ONU side is located between an optical splitter and an ONU.

The present invention discloses a device and a method for monitoring two-stage faults of a TDM-PON with high precision. A two-stage TDM-PON system includes an OLT I, a feeder fiber II, a stage-1 1:n optical splitter III, a stage-1 branch fiber IV, a stage-2 1:n optical splitter V, a stage-2 branch fiber VI, and an optical network unit (ONU) VII. A two-stage optical network monitoring system includes a monitoring part on the OLT I side and a monitoring part on the ONU VII side, where the monitoring part on the OLT I side includes a control-end isolator-free semiconductor laser, a control-end coupler, a control-end optical coupling device, a control-end photodetector, an integrated signal acquisition and processing device, and an optical coupling device; and the monitoring part on the ONU VII side is similar to the monitoring part of the OLT I side.

Embodiments relate to providing simultaneous digital and analog services in optical fiber-based distributed radio frequency (RF) antenna systems (DASs), and related components and methods. A multiplex switch unit associated with a head-end unit of a DAS can be configured to receive a plurality of analog and digital downlink signals from one or more sources, such as a service matrix unit, and to assign each downlink signal to be transmitted to one or more remote units of the DAS. In one example, when two or more downlink signals are assigned to be transmitted to the same remote unit, a wave division multiplexer/demultiplexer associated with the multiplex switch unit can be configured to wave division multiplex the component downlink signals into a combined downlink signal for remote side transmission and to demultiplex received combined uplink signals into their component uplink signals for head-end side transmission.

Methods, systems, and devices for network communications to reduce optical beat interference (OBI) in upstream communications are described. For example, a fiber node may provide a narrow band seed source to injection lock upstream laser diodes. Therefore, upstream communications from each injection locked laser diode may primarily include the wavelength associated with each seed source. The seed sources may be unique to each end device and configured to minimize OBI. That is, the upstream laser diodes may be generic, but the received seed source may enable upstream communications at varying wavelengths. The fiber node may provide each seed source by filtering (e.g., by a grating filter) a broadband light source.

The present invention discloses a device and a method for monitoring two-stage faults of a TDM-PON with high precision. A two-stage TDM-PON system includes an OLT I, a feeder fiber II, a stage-1 1:n optical splitter III, a stage-1 branch fiber IV, a stage-2 1:n optical splitter V, a stage-2 branch fiber VI, and an optical network unit (ONU) VII. A two-stage optical network monitoring system includes a monitoring part on the OLT I side and a monitoring part on the ONU VII side, where the monitoring part on the OLT I side includes a control-end isolator-free semiconductor laser, a control-end coupler, a control-end optical coupling device, a control-end photodetector, an integrated signal acquisition and processing device, and an optical coupling device; and the monitoring part on the ONU VII side is similar to the monitoring part of the OLT I side.

A method and apparatus for wavelength allocation for bidirectional optical access. The wavelength allocation method sets a first central wavelength for the optical path terminal to perform downstream transmission to the optical network unit, and a second central wavelength for the optical network unit to perform upstream transmission to the optical network terminal. At this time, the first center wavelength and the second center wavelength are separated by a predetermined wavelength interval, and the first center wavelength is set larger than the second center wavelength.

Optical network systems are disclosed, including a system comprising a transmitter including a digital signal processor operable to receive a plurality of independent data streams and output a plurality of digital signals based on the plurality of independent data streams, digital-to-analog circuitry operable to supply a plurality of analog signals based on the plurality of digital signals, a laser operable to supply an optical signal, a modulator operable to receive the optical signal and supply a modulated optical signal based on the plurality of analog signals, including a plurality of optical subcarriers, each of which being associated with a corresponding one of the plurality of independent data streams, a first one of the plurality of optical subcarriers having a first spectral width and a second one of the plurality of optical subcarriers having a second spectral width different than the first spectral width; and a first and a second receiver.

Digital information can be carried on the fiber leg of an access network using binary modulation. Binary modulated data received at an O/E node can then be modulated onto an analog waveform using quadrature amplitude modulation or some other technique for modulating an analog waveform and transmitted over, for example, the coaxial leg of the network. The O/E node may also receive an analog signal, over the coaxial leg, modulated to carry upstream data from subscriber devices. The O/E node may demodulate the upstream signal to recover the upstream data and forward that upstream data over the fiber leg using a binary modulated optical signal.

An ONU comprises a receiver configured to receive a continuous-mode TDMA downstream signal from an OLT; a PD coupled to the receiver and configured to convert the continuous-mode TDMA downstream signal to an electrical signal or an RF signal; an ADC coupled to the PD and configured to convert the electrical signal or the RF signal to a digital signal; and a burst-mode data recovery stage coupled to the ADC and configured to perform data recovery on a segment of the digital signal corresponding to the ONU, the burst-mode data recovery stage comprises a synchronization stage configured to perform synchronization on the segment.

The present disclosure provides a method and a device for controlling a downlink optical signal in a passive optical network, and a computer-readable storage medium. The method includes: monitoring power of a downlink optical signal in a process of receiving the downlink optical signal; and adjusting an attenuation value of a variable optical attenuator at an ONU side according to the power of the downlink optical signal until the power of the downlink optical signal falls within a preset power range. The variable optical attenuator at the ONU side is located between an optical splitter and an ONU.