An apparatus comprises: a first input tap; a first optical modulator coupled to the first input tap; a first output tap coupled to the first optical modulator so that the first optical modulator is positioned between the first input tap and the first output tap; and a controller indirectly coupled to the first input tap and the first output tap.

An optical transmitter includes: a splitter; a first optical modulator and a second optical modulator that modulate each of light beams split by the splitter; a first semiconductor optical amplifier (SOA) and a second SOA that are connected to a subsequent stage of the first optical modulator and a subsequent stage of the second optical modulator, respectively; a first detector and a second detector that detect light output intensity of the first SOA and light output intensity of the second SOA, respectively; a controller that sets gains of the first and second SOAs such that the first and second SOAs are equal in the light output intensity based on detection values of the first and second detectors; and a combiner that combines an output light beam of the first SOA and an output light beam of the second SOA.

An optical transmission apparatus includes an amplifier array device; and a switch device coupled to the amplifier array device via an optical cable, wherein the amplifier array device includes a plurality of amplifiers configured to amplify a plurality of optical signals at mutually different wavelengths and to output the plurality of amplified optical signals, a plurality of beam separators configured to generate a plurality of separated light beams by separating the plurality of amplified optical signals and to output the plurality of separated light beams, a beam combiner configured to generate combined light by combining the plurality of separated light beams and to output the combined light to the switch device through the optical cable, and a photo-detector configured to detect a power of the combined light returned from the switch device through the optical cable.

An optical transmission apparatus includes an amplifier array device; and a switch device coupled to the amplifier array device via an optical cable, wherein the amplifier array device includes a plurality of amplifiers configured to amplify a plurality of optical signals at mutually different wavelengths and to output the plurality of amplified optical signals, a plurality of beam separators configured to generate a plurality of separated light beams by separating the plurality of amplified optical signals and to output the plurality of separated light beams, a beam combiner configured to generate combined light by combining the plurality of separated light beams and to output the combined light to the switch device through the optical cable, and a photo-detector configured to detect a power of the combined light returned from the switch device through the optical cable.

An optical transmitter includes: optical modulation means; bias voltage output means for supplying the optical modulation means with a bias voltage on which a pilot signal is superimposed; pilot signal receiving means; and bias voltage control means. The bias voltage control means includes: training means for determining a control start voltage and a control direction of the bias voltage based on a pilot signal component at first and second bias voltage values; and feedback means for determining an appropriate bias voltage to compensate for a deviation of an operating point of the optical modulation means by analyzing the pilot signal component while adjusting the bias voltage in a stepwise fashion along the control direction from the control start voltage after the control start voltage and the control direction are determined.

An optical transmitter includes: optical modulation means; bias voltage output means for supplying the optical modulation means with a bias voltage on which a pilot signal is superimposed; pilot signal receiving means; and bias voltage control means. The bias voltage control means includes: training means for determining a control start voltage and a control direction of the bias voltage based on a pilot signal component at first and second bias voltage values; and feedback means for determining an appropriate bias voltage to compensate for a deviation of an operating point of the optical modulation means by analyzing the pilot signal component while adjusting the bias voltage in a stepwise fashion along the control direction from the control start voltage after the control start voltage and the control direction are determined.

An optical functional device equivalent to a 2×2 Mach-Zehnder optical switch is produced by forming two 3 dB couplers and input/output waveguides on a substrate. Two optical phase modulation paths are formed on corresponding waveguides between 3 dB couplers. A channel region having an opposite electric polarity is formed between source and drain regions, having the predetermined electric polarity, formed on the substrate. The optical phase modulation path is insulated from the surrounding area and disposed above the channel region. Additionally, a control electrode (i.e. a gate region) subjected to high-density doping is formed above the optical phase modulation path. By applying an electric voltage having the predetermined polarity to the control electrode, the source region, and the drain region, it is possible to generate hot carriers, in proximity to the optical phase modulation path, so as to accumulate charges and change a refractive index, thus setting a desired light-wave input/output path.

An optical functional device equivalent to a 2×2 Mach-Zehnder optical switch is produced by forming two 3 dB couplers and input/output waveguides on a substrate. Two optical phase modulation paths are formed on corresponding waveguides between 3 dB couplers. A channel region having an opposite electric polarity is formed between source and drain regions, having the predetermined electric polarity, formed on the substrate. The optical phase modulation path is insulated from the surrounding area and disposed above the channel region. Additionally, a control electrode (i.e. a gate region) subjected to high-density doping is formed above the optical phase modulation path. By applying an electric voltage having the predetermined polarity to the control electrode, the source region, and the drain region, it is possible to generate hot carriers, in proximity to the optical phase modulation path, so as to accumulate charges and change a refractive index, thus setting a desired light-wave input/output path.

A light transmitter to transmit multiple light packets, each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit. The light packets are transmitted at different start-times to establish different phases, one for each of the light packets, to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency. The light receiver samples the multiple light packets based on the sample timeline, to sample each received message at one of the different sample phases, then constructs a best series of bits based on the multiple demodulated messages.

A light transmitter to transmit multiple light packets, each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit. The light packets are transmitted at different start-times to establish different phases, one for each of the light packets, to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency. The light receiver samples the multiple light packets based on the sample timeline, to sample each received message at one of the different sample phases, then constructs a best series of bits based on the multiple demodulated messages.