An optical device includes an optical amplifier that optically amplifies incident light, a first isolator that is arranged on an input stage of the optical amplifier and inputs the incident light to the optical amplifier, and a second isolator that is arranged on an output stage of the optical amplifier and receives input of incident light that has been optically amplified by the optical amplifier. The first isolator inputs, to the optical amplifier, first linearly-polarized incident light that is converted from randomly-polarized incident light and that has been transmitted. The second isolator, when reflected light of the first linearly-polarized incident light that has been optically amplified by the optical amplifier is input from a reverse direction, converts reflected light of the first linearly-polarized incident light to reflected light of second linearly-polarized light that is orthogonal to the reflected light of the first linearly-polarized incident light.

A hyperspectral radiometer may comprise one or more antennas, a electro-optical modulator modulating the received RF signal onto an optical carrier to generate a modulated signal having at least one sideband; a filter filtering the modulated signal to pass the sideband to a photodetector; and a photodetector producing an electrical signal from which information of the RF signal can be extracted. In some examples, the optical sideband may be spatially dispersed to provide a plurality of spatially separate optical components to the photodetector, where the spatially separate optical components having different frequencies and correspond to different frequencies of the received RF signal. In some examples, the passed sideband may be mixed with an optical beam having a frequency offset from the optical carrier to form a combined beam having at least one optical signal component having a beat frequency from which information of the RF signal can be extracted.

Various embodiments of a monolithic transceiver are described, which may be fabricated on a semiconductor substrate. The monolithic transceiver includes a coherent receiver module (CRM), a coherent transmitter module (CTM), and a local oscillation splitter to feed a local oscillation to the CRM and the CTM with a tunable power ratio. The monolithic transceiver provides tunable responsivity by employing photodiodes for opto-electrical conversion. The monolithic transceiver also employs a polarization beam rotator-splitter (PBRS) and a polarization beam rotator-combiner (PBRC) for supporting modulation schemes including polarization multiplexed quadrature amplitude modulation (PM-QAM) and polarization multiplexed quadrature phase shift keying (PM-QPSK).

First compensation circuitry includes a first digital filter compensating a phase difference between a phase of a symbol of a received signal and a sampling timing, and first filter coefficient calculation circuitry calculating a filter coefficient of the first digital filter as a first filter coefficient. Second filter coefficient calculation circuitry calculates, as a second filter coefficient, a filter coefficient for adaptive equalization that compensates distortion due to temporally changing polarization dispersion, based on an output of the first digital filter. Coefficient combination circuitry combines the first filter coefficient and the second filter coefficient. Second compensation circuitry includes a second digital filter which uses a filter coefficient combined by the coefficient combination circuitry and performs a compensation of the phase difference between the phase of the symbol of the received signal and the sampling timing, and a process of the adaptive equalization at the same time.

An optical signal receiver includes a multimode waveguide for receiving a complex modulated optical signal, an optical resonator that receives the complex modulated optical signal from the multimode waveguide and converts the complex modulated optical signal to an intensity modulated signal, and a detector that is configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and that provides a detected signal.

A guided-wave-driven metasurface antenna includes an input for receiving a guided wave; an output for outputting a free-space wave; and a spatial frequency mixer connected between the input and the output for converting the guided wave to the free-space wave. The spatial frequency mixer is implemented by a metasurface of the antenna. The superheterodyne metasurface can be fabricated with high accuracy using lithography step similar to conventional waveguides made by the well-established semiconductor processing technology, making their integration with PICs straightforward.

A coherent optical transmitter includes circuitry connected to a coherent modulator; and a plurality of tunable optical filters (TOFs) connected to one another and connected to an output of the coherent modulator, wherein the plurality of tunable optical filters are configurable to create an effective transfer function having a variable width. The TOFs are cascaded and can be included in discrete form on electro-optic printed circuit boards (PCBs), or integrated in various electro-optic material systems such as in silicon photonics, photonic integrated circuits (PICs), as well as hybrid and other approaches. The advantage of this approach includes improved OSNR in colorless transmitters.

An optical reception apparatus (1) of the present invention includes: a local oscillator (11) outputting local oscillation light (22); an optical mixer (12) receiving a multiplexed optical signal (21) and the local oscillation light, and selectively outputting an optical signal (23) corresponding to the wavelength of the local oscillation light from the multiplexed optical signal; a photoelectric converter (13) converting the optical signal (23) output from the optical mixer into an electric signal (24); a variable gain amplifier (15) amplifying the electric signal (24) to generate an output signal (25) whose output amplitude is amplified to a certain level; a gain control signal generating circuit (16) generating a gain control signal (26) for controlling the gain of the variable gain amplifier (15); and a monitor signal generating unit (17) generating a monitor signal (27) corresponding to the power of the optical signal (23) using the gain control signal (26).

During operation, the system receives an optical input signal, and also receives a reference optical frequency comb (OFC) signal. Next, the system uses a gapless spectral demultiplexer to spectrally slice the optical input signal to produce a set of spectral slices. The system also uses a high-contrast demultiplexer to strongly isolate each combline of the reference OFC signal to produce a set of reference comblines. Next, in a parallel manner, the system demodulates each spectral slice in the set of spectral slices centered on a single reference combline in the set of reference comblines to produce a set of baseband I/Q signals, wherein each spectral slice is demodulated based on a known code sequence. The system then digitizes the set of baseband I/Q signals to produce a set of digitized signals. Finally, the system processes the set of digitized signals to directly reconstruct a waveform for the optical input signal.

A PIC including a plurality of optically interconnectable functional photonic blocks and a reconfigurable optical connection arrangement having a plurality of semiconductor-based optical waveguides and a plurality of controllable optical switches, at least one controllable optical switch being configurable to be in a first state allowing optical transmission or a second state preventing optical transmission. Depending on the respective first or second state of the at least one controllable optical switch, the optical connection arrangement is configured to enable at least a first set of semiconductor-based optical waveguides to provide at least one optical connection between at least two functional photonic blocks and/or a first optical access path to at least one functional photonic block. An opto-electronic system including the PIC and to a method of improved determination of an overall performance of the PIC.