An optical network includes an arrangement of optical nodes. An optical node of the arrangement, and corresponding method, perform optical connectivity discovery and negotiation-less optical fiber continuity verification in the optical network. An overall topology of optical connectivity provisioned for the arrangement is discovered by the optical node based on messages received from a management network communicatively coupling the optical nodes to each other. The optical node synchronizes, temporally and sequentially, with the other optical nodes based on the messages received, assigns fiber of the overall topology, based on a verification sequencing method, to verification slots of a verification sequence, and verifies continuity of fiber according to the verification slots of the verification sequence. The discovery, synchronization, and assignment operations enable the optical node and peer node to perform the optical fiber continuity verification in a symmetric, decentralized, and negotiation-less manner.

A phase-lock-free system includes a control instruction unit, a low-noise high-gain optical amplifier, an optical switch, a filter, an optical delay interferometer I, an optical delay interferometer Q, a first balanced detector, a second balanced detector, an anti-coding switch unit, a parallel-serial conversion unit, and a data processing unit. The control instruction unit is connected to the optical switch, the anti-coding switch unit, and the parallel-serial conversion unit, respectively; the low-noise high-gain optical amplifier is connected to the optical switch; the optical switch is connected to the first balanced detector and the second balanced detector by means of the filter, the optical delay interferometer I, and the optical delay interferometer Q, respectively. This system improves the compatibility of a communication system at a relay node in an existing laser communication network.

A telecommunications access network comprises a primary aggregation point in the form of an exchange, a plurality of optic fiber to metallic pair interface aggregation points which may be in the form of Distribution Point Units (DPUs) each of which is connected to the primary aggregation point by a respective optical fiber connection, and a plurality of terminating devices which may be in the form of customer premises equipment (CPE) devices, each of which is connected to a respective one of the optic fiber to metallic pair interface aggregation points by a respective twisted metallic pair connection. The access network further includes a plurality of metallic, interface-interface connections between one or more pairs of the optic fiber to metallic pair interface aggregation points. Each metallic, interface-interface connection preferably comprises three or more twisted metallic pairs of wires.

Transmitting devices used in an optical access system in which a plurality of the transmitting devices transmit an optical burst signal to a receiving device by time division multiple access, the transmitting devices each including an arithmetic processing unit, the arithmetic processing unit including: a data signal transmission instruction unit, the a data signal transmission instruction unit that outputs a first instruction for controlling transmission processing of a data signal on the basis of a requester's instruction; an optical signal control instruction unit that outputs a second instruction for controlling output processing of an optical signal on the basis of the requester's instruction; and an instruction output adjustment unit that adjusts a timing at which the first instruction is output and a timing at which the second instruction is output.

An optical network includes an arrangement of optical nodes. An optical node of the arrangement, and corresponding method, perform optical connectivity discovery and negotiation-less optical fiber continuity verification in the optical network. An overall topology of optical connectivity provisioned for the arrangement is discovered by the optical node based on messages received from a management network communicatively coupling the optical nodes to each other. The optical node synchronizes, temporally and sequentially, with the other optical nodes based on the messages received, assigns fiber of the overall topology, based on a verification sequencing method, to verification slots of a verification sequence, and verifies continuity of fiber according to the verification slots of the verification sequence. The discovery, synchronization, and assignment operations enable the optical node and peer node to perform the optical fiber continuity verification in a symmetric, decentralized, and negotiation-less manner.

Constellations of distributors interconnect access nodes to form a vast contiguous network. The access nodes are generally geographically spread and the constellations are generally geographically spread, however the distributors within each constellation are collocated. The access nodes are arranged into access groups. The access nodes of each access group interconnect through selected constellations, with each access node having a wavelength-division-multiplexed (WDM) link to each of the selected constellations, to form a three-stage network. The three-stage networks corresponding to the access groups are mutually fused so that an access node of any three-stage network has multiple paths, each traversing one distributor, to each other access node of the same three-stage network and a path to each other access node of the entire network traversing one distributor. The distributors are preferable configured as fast optical switches. The network is structured to provide global coverage without the need for conventional cross-connectors.

In an aspect, an apparatus for distribution of frequency reference to a receiving end over a transmission medium comprises a first mixer adapted to mix a frequency reference signal having a reference frequency with a local oscillator signal having a local oscillator frequency to provide a forward frequency reference signal, a communication section adapted to transmit the forward frequency reference signal and receive a first backward frequency reference signal, a second mixer adapted to mix the first backward frequency reference signal with the local oscillator signal to provide a second backward frequency reference signal and a phase comparator and control circuit adapted to adjust the local oscillator frequency based on a phase shift of the second backward frequency reference signal so as to compensate for a phase shift of the forward frequency reference signal.

A master unit configured to manage a plurality of remote units connected in a ring topology, the master unit comprising: a network management section configured to transmit at least one of a path-state monitoring control signal and a delay measurement control signal to the plurality of remote units in a first direction and a second direction which is a reverse direction of the first direction, and receives an acknowledgement signal in response to the at least one of a path-state monitoring control signal and a delay measurement control signal; and switching control means for transmitting a forward signal received from a base station in the first direction, and transmitting a switching control signal in the second direction when a defect is detected in any remote unit among the plurality of remote units by the network management section.

An optical module for use in an optical system is disclosed, the optical module implementing Precision Time Protocol (PTP) clock functionality therein. The optical module includes an electrical interface with the optical system; circuitry connected to the electrical interface and configured to implement a plurality of functions of functionality; an optical interface connected to the circuitry; and timing circuitry connected to the electrical interface and one or more of the plurality of functions, wherein the timing circuitry is configured to implement the PTP clock functionality.

In various embodiments, a method is provided. In this method, a first signal is received from a master node, and is sampled to obtain a first sample. The first sample is then quantized to obtain a quantized form of the first sample. A first synchronization sequence is detected from the quantized form of the first sample at T2. First information is received from the master node and the first information is used to indicate a moment T1 at which the master node sends the first synchronization sequence. A second synchronization sequence is sent to the master node at T3. Second information received from the master node and the second information is used to indicate a moment T4 at which the master node detects a quantized form of the second synchronization sequence. Time synchronization is performed based on T1, T2, T3, and T4.