Embodiments relate to a free space optical (FSO) terminal that transmits and receives optical beams. The FSO terminal includes a fore optic and a rotatable dispersive optical component. A receive (Rx) optical beam from the remote FSO communication terminal is received through the fore optic, and a transmit (Tx) optical beam is transmitted through the fore optic. The dispersive optical component is positioned along the optical paths of both the Rx and Tx optical beams. Since the Rx and Tx optical beams have different wavelengths and the dispersive optical component has a wavelength dependence, the dispersive optical component creates an angular separation between the Rx and Tx optical beams. The controller controls the rotational position of the dispersive optical component (and possibly also the wavelength of the Tx optical beam) to achieve a desired angular separation between the Rx and Tx optical beams.

The optical element for a low frequency band includes a substrate including a first main face and a second main face, the substrate having birefringence, and an antireflection film located on the first main face, wherein the low frequency band is lower than a reststrahlen band of the antireflection film, wherein an absolute value of a difference between a first refractive index and a second refractive index of the substrate in the low frequency band is 0.2 or more, and wherein a thickness of the substrate is 15 μm or more and 4000 μm or less.

The present invention provides an apparatus for facilitating a photovoltaic device to provide a wireless communication channel. The apparatus comprises a switch connected in parallel with the photovoltaic device and configured for driving the photovoltaic device to produce optical signals carrying sensed data to be transmitted; and a control module connected with the switch and configured for receiving electrical sensing signals and generate a control signal to control the switch. The apparatus provided by the present invention is extremely durable. Compared to existing communication technologies which require extra hardware, the apparatus provided by the present invention is simpler and can be integrated into a single component.

The present invention provides an apparatus for facilitating a photovoltaic device to provide a wireless communication channel. The apparatus comprises a switch connected in parallel with the photovoltaic device and configured for driving the photovoltaic device to produce optical signals carrying sensed data to be transmitted; and a control module connected with the switch and configured for receiving electrical sensing signals and generate a control signal to control the switch. The apparatus provided by the present invention is extremely durable. Compared to existing communication technologies which require extra hardware, the apparatus provided by the present invention is simpler and can be integrated into a single component.

A method and an apparatus are described that split a broadband optical signal into a plurality of narrow-band portions. Each of said narrow-band portions is combined in the same optical channel with an optical local oscillator (OLO). Furthermore, the OLO is spectrally separate from, or non-overlapping with, the corresponding narrow-band portion of the signal in the same channel. This functionality is achieved by launching the broadband optical signal and a local oscillator optical comb (LOOC) into separate waveguides at the input star coupler of an arrayed-waveguide grating. The waveguides of the output star coupler carry the narrow-band portions of the broadband optical signal along with the respective non-overlapping spectral lines of the OLO.

An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

Techniques (e.g., method, apparatuses, etc.) for permitting communications, e.g., optical communications are described. In one example, a first communication apparatus may send a bit allocation table, BAT, message, to a second communication apparatus. The BAT update information has a BAT update information signalling update information for updating a BAT which is signalled to be updated. The BAT update information groups information into different groups of subcarriers, wherein the BAT update information has, for each group of subcarriers, information indicating the number of carriers in the group.

Techniques (e.g., method, apparatuses, etc.) for permitting communications, e.g., optical communications are described. In one example, a first communication apparatus may send a bit allocation table, BAT, message, to a second communication apparatus. The BAT update information has a BAT update information signalling update information for updating a BAT which is signalled to be updated. The BAT update information groups information into different groups of subcarriers, wherein the BAT update information has, for each group of subcarriers, information indicating the number of carriers in the group.

Embodiments relate to a free space optical (FSO) terminal that transmits and receives optical beams. The FSO terminal includes a fore optic and a rotatable dispersive optical component. A receive (Rx) optical beam from the remote FSO communication terminal is received through the fore optic, and a transmit (Tx) optical beam is transmitted through the fore optic. The dispersive optical component is positioned along the optical paths of both the Rx and Tx optical beams. Since the Rx and Tx optical beams have different wavelengths and the dispersive optical component has a wavelength dependence, the dispersive optical component creates an angular separation between the Rx and Tx optical beams. The controller controls the rotational position of the dispersive optical component (and possibly also the wavelength of the Tx optical beam) to achieve a desired angular separation between the Rx and Tx optical beams.