A laser communication system for an aircraft has optical head units, separate laser transmitting unit, laser receiving unit, optical fiber for each optical head unit, optical switching device for coupling an optical head unit and a separate laser transmitting unit, and a central control unit, the optical head units connected to the optical switching device through the optical fiber, the optical head units having an optical axis, parallel to which light is emitted or received, and an optical pointing mechanism for adjusting the respective optical axis. The separate laser transmitting unit has a laser. The control unit connects to the optical switching device, laser transmitting unit, laser receiving unit and optical head unit to control a laser based data communication through coupling an optical head unit, which is in a free line of sight to a target outside the aircraft, to the laser transmitting unit and to modulate operation of the laser transmitting unit for emitting a signal.

An emitter configured to output a sequence of periodic light pulses with different polarisations, the emitter comprising:

a beam splitter configured to divide the pulses of a first sequence of pulses, such that each pulse is split between a first path and a second path, the first sequence of pulses having a varying phase and a first polarisation;

a polarisation rotator configured to rotate the polarisation state of pulses in one of the first path or the second path with respect to the polarisation state of pulses in the other path;

a time delay component configured to provide a time delay such that the first sequence of pulses in the first arm are delayed by one period with respect to the first sequence of pulses in the second arm;

an optical combination component configured to combine the delayed first sequence of pulses from the first path with the first sequence of pulses from the second path to produce an output sequence of pulses where each pulse in the output sequence is a combination of a pulse from the second path and a delayed pulse from the first path and has a polarisation determined from the phase difference between combined pulses and the polarisation of the first path and the second path.

In a general aspect, a communication system comprises a first station and a second station. The first station includes a photonic crystal maser, a laser subsystem, and a tracking subsystem. A photonic crystal structure of the photonic crystal maser is formed of dielectric material and has an array of cavities and an elongated slot. The elongated slot is disposed in a defect region of the array of cavities. The photonic crystal maser also includes a vapor disposed in the elongated slot and operable to emit a target RF electromagnetic radiation in response to receiving an optical signal. The array of cavities and the elongated slot define a waveguide configured to form the target RF electromagnetic radiation, when emitted, into a beam. The second station includes a receiver configured to couple to the beam of target RF electromagnetic radiation.

A high-speed optical transceiver integrated chip drive circuit with phase delay compensation function includes a transmitting end drive circuit to drive the laser to emit light to transmit signals and a receiving end drive circuit to optimize the signal degradation caused by the signal sent by the transmitting end drive circuit to the laser via the transmission backplane; a long code phase lead adjustment circuit is arranged on the main channel of the transmitting end drive circuit, and a long code phase lag adjustment circuit is set on the main channel of the receiving end drive circuit. The present invention is used to optimize high-speed signals and solve the problem that the CML drive circuit at the receiving end or the laser drive circuit at the transmitting end cannot compensate the difference between the group delay and phase delay for the high-speed signal after passing through the backplane (Laser device).

A diverged beam optical transmitter is provided that includes a laser source configured to emit a light beam, and one or more lenses. The diverged beam optical transmitter also includes a diffuser placed between the laser source and the one or more lenses, and configured to increase an intrinsic divergence of the light beam and to fill some portion of the one or more lenses such that the light beam is eye safe after the one or more lenses.

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 tunable laser includes a reflective semiconductor optical amplifier (SOA), a grating codirectional coupler, and a reflective microring resonator. The grating codirectional coupler and the reflective microring resonator are both formed on a silicon base. An anti-reflection film is disposed on a first end surface of the reflective SOA, and the first end surface is an end surface, coupled to a first waveguide of the grating codirectional coupler, of the reflective SOA. A second waveguide of the grating codirectional coupler is coupled to the first waveguide, a first grating is disposed on the first waveguide, a second grating disposed opposite to the first grating is disposed on the second waveguide, and the first grating and the second grating constitute a narrow-band pass filter. The second waveguide is connected to the reflective microring resonator.

An apparatus includes an optical splitter configured to receive an optical signal and to split the input optical signal to provide a first and a second optical signal. The apparatus further includes an interferometer comprising a first arm and a second arm, with the first arm being configured to receive the first optical signal, and the second arm being configured to receive the second optical signal. Notably a portion of the first arm is exposed to a reference gas that attenuates light of a characteristic wavelength. The apparatus further includes an optical coupler configured to receive an output optical signal from the first arm, and an output optical signal from the second arm and to provide a third optical signal; and a photodetector configured to receive the third optical signal, and to provide a photocurrent. The photocurrent increases when the difference between the characteristic wavelength and the wavelength of the optical signals increases. The apparatus also comprises a feedback control circuit configured to change the properties of the laser to be locked until an error signal indicative of the difference between the characteristic wavelength and the wavelength of the laser is substantially zero.

A distributed antenna system comprises: one or more access units configured to receive multiple downlink radio frequency signal sets, and further configured to convert the multiple downlink radio frequency signal sets into multiple downlink optical signal sets; a first wavelength division multiplexing unit configured to multiplex the multiple downlink optical signal sets to generate a first wavelength division multiplexing optical signals; a first wavelength division demultiplexing unit configured to demultiplex the first wavelength division multiplexing optical signals to obtain the multiple downlink optical signal sets; a first optical fiber, coupled between the first wavelength division multiplexing unit and the first wavelength division demultiplexing unit, and configured to transmit the first wavelength division multiplexing optical signal; and multiple first remote units coupled to the first wavelength division multiplexing unit, and configured to convert the multiple downlink optical signal sets into the multiple downlink radio frequency signal sets for transmission.

An optical emitter comprising a primary laser and a plurality of secondary lasers wherein each secondary laser is optically injection locked to said primary laser, the emitter further comprising at least one polarisation controller configured to control the polarisation of the output of at least one of the secondary lasers, the emitter further comprising a combination unit that is configured to combine the outputs of the secondary laser modules into an output signal.