A pump laser package may include an input fiber to send signal light on a first optical path inside a package, a source to send pump light on a second optical path inside the package, and an output fiber on a third optical path inside the package. The pump laser package may include a WDM filter inside the package to receive the signal light on the first optical path and send the signal light on the third optical path, and receive the pump light on the second optical path and send the pump light on the third optical path. The pump laser package may include an isolator inside the package to transmit the signal light in a first direction, and block the signal light in a second direction, or a photo-diode to receive a portion of the signal light sent on a fourth optical path.

Consistent with an aspect of the present disclosure, electrical signals or digital subcarriers are generated in a DSP based on independent input data streams. Drive signals are generated based on the digital subcarriers, and such drive signals are applied to an optical modulator, including, for example, a Mach-Zehnder modulator. The optical modulator modulates light output from a laser based on the drive signals to supply optical subcarriers corresponding to the digital subcarriers. These optical subcarriers may be received by optical receivers provided at different locations in an optical communications network, where the optical subcarrier may be processed, and the input data stream associated with such optical subcarrier is output. Accordingly, instead of providing multiple lasers and modulators, for example, data is carried by individual subcarriers output from an optical source including one laser and modulator. Thus, a cost associated with the network may be reduced. Moreover, each of the subcarriers may be detected by a corresponding one of a plurality of receivers, each of which being provided in a different location in the optical communication network. Thus, receivers need not be co-located, such that the network has improved flexibility.

An optical receiver, used in wavelength-division multiplexing, has multiple photodetectors per channel. The optical receiver comprises a demultiplexer to separate incoming light into different output waveguides, one output waveguide for each channel. A splitter is used in each output waveguide to split each output waveguide into two or more branches. A separate photodetector is coupled with each branch so that two or more photodetectors are used to measure each channel.

Embodiments describe optical imagers that include one or more micro-optic components. Some imagers can be passive imagers that include a light detection system for receiving ambient light from a field. Some imagers can be active imagers that include a light emission system in addition to the light detection system. The light emission system can be configured to emit light into the field such that emitted light is reflected off surfaces of an object in the field and received by the light detection system. In some embodiments, the light detection system and/or the light emission system includes micro-optic components for improving operational performance.

The present invention is directed to a communication signal tracking system comprising an optical receiver including one or more delay line interferometers (DLIs) configured to demultiplex incoming optical signals and a transimpedance amplifier configured to convert the incoming optical signals to incoming electrical signals. The communication signal tracking system further includes a control module configured to calculate a bit-error-rate (BER) of the incoming electrical signals before forward-error correction decoding, and use the BER as a parameter for optimizing settings of the one or more DLIs in one or more iterations in a control loop and generating a back-channel data.

A second transceiver (22) includes a guide light source (22c), a photorefractive crystal (22a), and a frequency control unit (22e). The guide light source (22c) emits guide light (Y3). A double phase conjugate mirror (22m) is formed in a crystal (22a) by scattering of reference signal light (Y1), which has a frequency different from that of the guide light and is incident on the crystal via space (15) after being transmitted from a first transceiver (21) which is a transceiver on the other side, and the guide light that is incident on the crystal in a reverse direction to that of the reference signal light. A frequency control unit (22e) couples the reference signal light emitted from the crystal (22a), which is phase-conjugate light of the guide light generated by the mirror (22m), to an optical fiber (13b).

An embodiment method includes multiplexing light emitted by the plurality of optical transmitters to provide a multiplexed optical signal; propagating the multiplexed optical signal through an optical interleaver from a first port thereof to a combined port thereof and back to a second port thereof; and detecting an optical signal at the second port of the optical interleaver.

The present invention is directed to a communication signal tracking system comprising an optical receiver including one or more delay line interferometers (DLIs) configured to demultiplex incoming optical signals and a transimpedance amplifier configured to convert the incoming optical signals to incoming electrical signals. The communication signal tracking system further includes a control module configured to calculate a bit-error-rate (BER) of the incoming electrical signals before forward-error correction decoding, and use the BER as a parameter for optimizing settings of the one or more DLIs in one or more iterations in a control loop and generating a back-channel data.

A receiver assembly (1) has a radiation guide (4) having an elongate form. The length is at least five times longer than all dimensions of the radiation guide perpendicular to the longitudinal axis (3). The guide receives radiation via an outer lateral surface (8), converts the radiation to longer wavelength radiation, and guides the converted radiation to a longitudinal end surface (2). A receiver unit (5) receives radiation output from the longitudinal end surface.

The receiving-side system (10) includes a smaller number of optical reception front ends (12) than the number of a plurality of wavelength-multiplexed subcarrier signals. Each of the optical reception front ends (12) is configured to receive two or a plurality subcarrier signals of the plurality of subcarrier signals. A frequency offset monitoring unit (22) monitors frequency offsets of the respective subcarrier signals received by the optical reception front end (12). A light source frequency control unit (24) controls at least one of a light source frequency of the transmitting-side system (2) and a light source frequency of the receiving-side system (10) based on a result of the monitoring performed by the frequency offset monitoring unit (22).