A decoding system, a decoding controller, and a decoding control method are provided. In the decoding system, a decoding controller is disposed between two adjacent decoders. The decoding controller determines whether to perform turn-off based on a non-turn-off indication received by a previous-stage decoder, a turn-off indication output by the previous-stage decoder, and historical turn-off probability statistics. This is equivalent to adding a buffer zone between the two adjacent decoders.

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.

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.

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.

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 short-waveband active optical component based on a vertical emitting laser and a multi-mode optical fiber has an emitting end and a receiving end. In the emitting end, multiple VCSELs generate multiple optical signals of different wavelengths, and multiple photodiodes in the receiving end receive the optical signals emitted by the VCSELs. Both ends use a focusing lens array to collimate and focus the optical signals A Z-block-shaped prism performs a light combining function at the emitting end, while another Z-block-shaped prism performs a light splitting function at the receiving end. Both ends use a focusing lens for collimating and focusing the optical signals at ends of a multi-mode optical fiber, which is used for transmitting the optical signals generated by the VCSELs. The short-waveband active optical component has a small size and a high transmission rate.

A short-waveband active optical component based on a vertical emitting laser and a multi-mode optical fiber has an emitting end and a receiving end. In the emitting end, multiple VCSELs generate multiple optical signals of different wavelengths, and multiple photodiodes in the receiving end receive the optical signals emitted by the VCSELs. Both ends use a focusing lens array to collimate and focus the optical signals A Z-block-shaped prism performs a light combining function at the emitting end, while another Z-block-shaped prism performs a light splitting function at the receiving end. Both ends use a focusing lens for collimating and focusing the optical signals at ends of a multi-mode optical fiber, which is used for transmitting the optical signals generated by the VCSELs. The short-waveband active optical component has a small size and a high transmission rate.

A device may include: a highly doped n.sup.+ Si region; an intrinsic silicon multiplication region disposed on at least a portion of the n.sup.+ Si region, the intrinsic silicon multiplication having a thickness of about 90-110 nm; a highly doped p.sup.− Si charge region disposed on at least part of the intrinsic silicon multiplication region, the p.sup.− Si charge region having a thickness of about 40-60 nm; and a p.sup.+ Ge absorption region disposed on at least a portion of the p.sup.− Si charge region; wherein the p.sup.+ Ge absorption region is doped across its entire thickness. The thickness of the n.sup.+ Si region may be about 100 nm and the thickness of the p.sup.− Si charge region may be about 50 nm. The p.sup.+ Ge absorption region may confine the electric field to the multiplication region and the charge region to achieve a temperature stability of 4.2 mV/° C.