Systems and methods to transmit audio-video signals over an optical communication channel are described. One aspect includes receiving a plurality of audio-video electrical signals at an optical transmitter. The optical transmitter may also receive a plurality of out-of-band electrical signals. The optical transmitter may collectively modulate the audio-video electrical signals to generate a composite electrical signal. In one aspect, the optical transmitter bias current-modulates a bias current level of the composite electrical signal using the electrical out-of-band signals, and generates a modulated electrical signal based on the bias current-modulating. The optical transmitter may convert the modulated electrical signal into a modulated optical signal using a laser diode, and transmit the modulated optical signal to an optical receiver over an optical communication channel.

A transmission method includes: in a first period, causing a light source to emit light having a first luminance; and in a second period, causing the light source to transmit an optical signal by causing the light source to alternately emit light having a second luminance and light having a third luminance lower than the second luminance.

A system and method for analog estimation of a spectral correlation function (SCF) provides a photonic carrier to generate a signal comb and offset comb, each comprising N comb tones separated by respective repetition rates ΔF and ΔF+δF. The signal and offset combs are amplitude-modulated according to an inbound RF signal of interest and filtered via periodic optical filters to produce a sequence of N Fourier components of the signal comb and N Fourier components of the offset comb, each filtered signal comb component overlapping with a filtered offset comb component. In-phase/quadrature (I/Q) components of the products of each component of the complex conjugate of the filtered offset comb and the overlapping counterpart of the filtered signal comb are generated in an optical receiver and digitized into slices of the SCF at a fixed time instance and center frequency, correlated at various cyclic separations α.

This disclosure describes digitally generating sub-carriers (SCs) to provide isolation and dynamic allocation of bandwidth between uplink and downlink traffic between transceivers that are communicatively coupled via a bidirectional link including one or more segments of optical fiber. Separate uplink and downlink communication channels may be created using digitally generated SCs and using the same transmitter laser. In some implementations, one or more of the nodes include a transceiver having at least one laser and one digital signal processing (DSP) operable for digitally generating at least two SCs and detecting at least two SCs. The transceiver can transmit selected SCs, and can receive other SCs. Accordingly, the transceiver can facilitate bidirectional communication, for example, over a single optical fiber link. In some instances, techniques can facilitate dynamic bandwidth assignment by facilitating adding or blocking of optical subcarriers from transmission in an uplink or downlink direction.

In order to make a communicable distance in an optical cable of an optical signal which is subjected to amplitude modulation longer, a re-modulation device is provided with: an acquisition unit that acquires, from a first modulation optical signal obtained by performing first amplitude modulation on an optical signal with second data sent from a modulation transmission device to a demodulation reception device, the second data; and a re-modulation unit that, when determining passing of the first modulation optical signal, sends, to the demodulation reception device, a second modulation optical signal obtained by performing second amplitude modulation on the inputted optical signal with the second data.

A method including transmitting an intensity-modulated light through a mode conditioner to generate a mode-conditioned intensity-modulated light in one or a plurality of launch conditions and transmitting the mode-conditioned intensity-modulated light through a multimode optical fiber under test (FUT) to excite a plurality of modes of the FUT. The method further includes converting the mode-conditioned intensity-modulated light transmitted through the FUT into an electrical signal, measuring, based on the electrical signal, a complex transfer function CTF(f) of the FUT, and obtaining an output pulse based on the measured complex transfer function CTF(f) from one or a plurality of launch conditions and an assumed input pulse using the equation: P.sub.out (t)=.sup.−1(CTF(f)*(P.sub.in(t))). Wherein, P.sub.out (t) is the output pulse, .sup.−1(CTF(f)*(P.sub.in(t))) is the inverse Fourier transform of the function CTF(f)*(P.sub.in (t)), and (P.sub.in(t)) is the Fourier transform of the assumed input pulse. Additionally, the method includes calculating modal bandwidth of the FUT based on P.sub.out(t).

An optical IQ modulator includes: Y branching elements, which are cascade-connected, each of which has one input and two outputs; QPSK modulators configured to perform QPSK modulation on continuous light branched by the Y branching elements to generate signal light; and Y combining elements, which are cascade-connected, each of which has two inputs and one output.

An electronic device may include an antenna that conveys wireless signals at frequencies greater than 100 GHz. The antenna may include a radiating element coupled to a uni-travelling-carrier photodiode (UTC PD). An optical path may illuminate the UTC PD using a first optical local oscillator (LO) signal and a second optical LO signal. An optical phase shift may be applied to the first optical LO signal. A Mach-Zehnder modulator (MZM) may be interposed on the optical path. During signal transmission, the MZM may modulate wireless data onto the second optical LO signal while control circuitry applies a first bias voltage to the UTC PD. During signal reception, the control circuitry may apply a second bias voltage to the UTC PD that configures the UTC PD to convert received wireless signals into intermediate frequency signals and/or optical signals.

An apparatus includes an optical source of an optical wavelength carrier, an optical modulator to receive the optical wavelength carrier, and an optical data receiver. The optical data modulator is configured to produce, from the optical wavelength carrier, an optical signal to carry separate data on different first and second components thereof in individual modulation periods during data transmission and to carry a training sequence on one of the components during time slots for calibration. The first component is relatively phase offset from the second component in the optical signal. The optical data modulator alternates the one of the components between the first and second components over the time slots for calibration. The optical receiver is connected to receive a portion of the optical signal and to temporally interleave a measurement of a characteristic of the first component and a measurement of a characteristic of the second component over the time slots for calibration. The optical receiver is configured to feedback information to the optical data modulator based on the measured characteristics. The optical data modulator is configured to reduce an imbalance between the two components of the optical carrier during data transmission based on the information.

An optical transmitter based on optical time division multiplexing is disclosed, which may solve the issues of complex structure and operation of a multilevel-OTDM-based optical transmitter while using a multilevel signal modulation format and OTDM technology that may increase the transmission rate of an optical transmitter with limited bandwidth.