The performance of quantum key distribution by systems and methods that use wavelength division multiplexing and encode information using both wavelength and polarization of photons of two or more wavelengths. Multi-wavelength polarization state encoding schemes allow ternary-coded digits, quaternary-coded digits and higher-radix digits to be represented by single photons. Information expressed in a first radix can be encoded in a higher radix and combined with a string of key values to produce a datastream having all allowed digit values of that radix in a manner that allows eavesdropping to be detected without requiring the sender and receiver to exchange additional information after transmission of the information.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.

There are provided a communication device, a communication system, and a communication method. A communication device includes a first receiver configured to receive a data signal and generate a level control signal based on an initial level of the data signal and on an error rate of the data signal; and a transmitter configured to transmit the level control signal.

The present invention discloses an optical signal frequency calibration method and device. The method includes: receiving a first optical signal that experiences a frequency offset and that is generated by a laser in a transmitter of an access node; receiving a reference optical signal sent by a local oscillator; calculating a difference between a specified frequency difference and a frequency difference between the reference optical signal and the first optical signal; and performing frequency calibration on the first optical signal according to the difference, modulating to-be-sent uplink data by using the calibrated first optical signal, and sending the modulated uplink data to a primary node.

Aspects of the present disclosure aim at configuring an optical time domain reflectometry (OTDR) in a central office such that the OTDR is configured to be operatively coupled with and also configured to periodically poll each fiber at defined intervals and compute/store a reflection signature that can be used to compare with future signatures received from subsequent polls of the fiber to determine a fault (e.g., a fiber cut or breakage) between the central office (CO) and one or more optical network unit (ONU) over GIS.

Methods, systems, and apparatus for communicating over a radio link by devices with broadband connectivity are disclosed. In one aspect, a telecommunications device includes a first transceiver, a second transceiver, and a state monitor. The first transceiver communicates over a broadband link. The second transceiver communicates over a radio link. The radio link is a Low-Power Wide-Area Network (LPWAN) link. The state monitor includes one or more processes that monitor a state of the telecommunications device, and in response to the state of the telecommunications device being one of a plurality of pre-specified states, transmit, using the second transceiver, data specifying the state of the telecommunications device over the radio link.

There are provided an optical fiber display system and an optical fiber changeover method each enabling an efficient optical fiber changeover work. The optical fiber display system according to the present invention includes a plurality of core wire identification terminals 101. Each of the core wire identification terminals 101 includes: bent part formation units 11 configured to form a bent part at an optional position of an optical fiber 50 and to leak optical signals propagating through the optical fiber 50 from the bent part; analysis units 12 configured to acquire identification numbers of communication apparatuses (51 and 52) included in the leaked optical signals, the communication apparatuses (51 and 52) being connected to respective ends of the optical fiber 50; a communication unit 13 configured to inquire of a database 201 storing relationship between the optical fiber and the communication apparatuses about the acquired identification numbers of the communication apparatuses, and to receive an identification number of the optical fiber 50 corresponding to the acquired identification numbers of the communication apparatuses, from the database 201; and a display unit 14 configured to display the acquired identification numbers of the communication.

Aspects of a method and system for high-speed, low-power optical communications are provided. In one embodiment, a system for optical communications comprises a digital-to-analog converter (DAC), a driver, and a transmit optical subsystem. The DAC is operable to receive a digital code of a plurality of digital codes and output an analog current signal having an analog current level of a plurality of analog current levels. The driver is operable to condition the analog current signal output from the digital-to-analog converter. The transmit optical subsystem is operable to generate an optical power signal from the conditioned analog current signal. A mapping between the plurality of digital codes and the plurality of analog current levels is dynamically controlled according to one or more characteristics of the optical power signal. The one or more characteristics comprise or a symbol amplitude sensitivity and/or a nonlinearity that may be temperature dependent.

A method and apparatus for automatic determination of a fiber type of at least one optical fiber span used in a link of an optical network, the method comprising the steps of measuring a length of said optical fiber span; measuring a chromatic dispersion of said optical fiber span; determining a fiber dispersion profile of said optical fiber span on the basis of the measured length and the measured fiber chromatic dispersion; and determining a fiber category and/or a specific fiber type of said optical fiber span depending on the determined fiber dispersion profile.

A method and apparatus for automatic determination of a fiber type of at least one optical fiber span used in a link of an optical network, the method comprising the steps of measuring a length of said optical fiber span; measuring a chromatic dispersion of said optical fiber span; determining a fiber dispersion profile of said optical fiber span on the basis of the measured length and the measured fiber chromatic dispersion; and determining a fiber category and/or a specific fiber type of said optical fiber span depending on the determined fiber dispersion profile.