A laser light source includes an inner ring and an outer ring. The inner ring includes a semiconductor optical amplifier (SOA), a pair of optical circulators, a first optical filter, and a first optical waveguide connecting those in series. The outer ring includes the SOA, a pair of optical circulators, a second optical filter, an output port, and a second optical waveguide connecting those in series except for a portion shared. The inner ring operates as a gain-clamped SOA with a feedback control light defined by the first optical filter. The outer ring generates a laser output in a gain region of the clamped SOA, and with multiple peak wavelengths defined by the second optical filter, in a range from L Band to U band, applicable to WDM network systems. A WDM network system and a method of controlling the laser light source are also disclosed.

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 optical transmitter according to one embodiment includes a housing with an emission end, a light emitting element mounted on a first mounting portion of the housing, and a light receiving element mounted on a second mounting portion of the housing to monitor output light from the light emitting element. The second mounting portion is provided with a carrier, a first resin located on an emission end side of a lower side of the carrier, and a second resin located on a light emitting element side of the lower side of the carrier. A coefficient of thermal expansion of the first resin is smaller than a coefficient of thermal expansion of the second resin.

A downhole optical communications system provided at a downhole location in use, the downhole communications system being for communicating between the downhole location and an uphole location, such as a surface location. The downhole optical communications system comprises a downhole optical transmitter configured to emit an optical signal for transmission over an optical transmission channel between the uphole location and the downhole optical transmitter; wherein the downhole optical transmitter is configured so as to produce a response to an optical signal received from the optical transmission channel and the downhole optical communications system is configured to determine data represented by the received optical signal from the response produced by the downhole optical transmitter.

A downhole optical communications system provided at a downhole location in use, the downhole communications system being for communicating between the downhole location and an uphole location, such as a surface location. The downhole optical communications system comprises a downhole optical transmitter configured to emit an optical signal for transmission over an optical transmission channel between the uphole location and the downhole optical transmitter; wherein the downhole optical transmitter is configured so as to produce a response to an optical signal received from the optical transmission channel and the downhole optical communications system is configured to determine data represented by the received optical signal from the response produced by the downhole optical transmitter.

An optical network communication system utilizes a passive optical network (PON) and includes an optical line terminal (OLT) having a downstream transmitter and an upstream receiver, and an optical network unit (ONU) having a downstream receiver and an upstream transmitter. The downstream transmitter is configured to provide a coherent downlink transmission, and the downstream receiver is configured to obtain one or more downstream parameters from the coherent downlink transmission. The system further includes a long fiber configured to carry the coherent downlink transmission between the OLT and the ONU. The ONU is configured to communicate to the OLT a first upstream ranging request message, the OLT is configured to communicate to the ONU a first downstream acknowledgement in response to the upstream first ranging request message, and the ONU is configured to communicate to the OLT a second upstream ranging request message based on the first downstream acknowledgement.

A method for automatic power and modulation management in a communication network includes (1) generating a management function of (a) mutual information per symbol (MIPS) of the communication network and (b) output power (P) of a transmitter of the communication network, determining a selected MIPS value and a selected P value which achieve a maximum value of the management function, and causing the transmitter of the communication network to operate according to the selected MIPS value and the selected P value.

Disclosed are an optical device capable of precise adjustment of optical output intensity, and a method for manufacturing an optical device. An optical device including a laser diode, according to one aspect of the present embodiment, comprises: a laser diode for outputting light having a predetermined wavelength; an optical output unit in which output light of the laser diode is optically coupled and the output of the optical device takes place; and an optical isolator disposed between the laser diode and the optical output unit. The output light of the laser diode passes through the optical isolator and the output of the optical device takes place through the optical output unit, and the intensity of the output light of the optical device is determined by the rotation of the optical isolator.

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.

An optical modulator includes a waveguide layer, an electro-optical material layer, and electrodes. The waveguide layer includes a sub-wavelength waveguide; the electro-optical material layer is disposed on a surface of the sub-wavelength waveguide, and the sub-wavelength waveguide is configured to diffuse a light field at the waveguide layer into the electro-optical material layer; the electrodes are disposed on a surface of the electro-optical material layer, and a connection line between the electrodes is parallel to a plane on which the electro-optical material layer is located, or the electrodes are disposed on two sides of the electro-optical material layer, and a connection line between the electrodes intersects with a plane on which the electro-optical material layer is located; and the electrodes are configured to apply an electrical signal to the electro-optical material layer.