The present technology relates to a transmission apparatus, a transmission method, and a filter circuit that make it possible to transmit a signal with high quality, the signal including a plurality of signals having different speeds. The transmission apparatus includes a detection unit that detects each of a plurality of signals having different speeds from an input signal. Further, the transmission apparatus includes an output control unit that controls output of an output signal including the plurality of signals, on the basis of detection results of the plurality of signals by the detection unit. The present technology can be applied to, for example, a transmission apparatus that transmits a serial signal conforming to the USB 3.0 standards or a transmission apparatus that converts the serial signal described above into a millimeter-wave signal or an optical signal and sends and receives the signal.

A data carrier 2 is provided with a comparator 41, a capacitor 42, a comparator operation adjustment resistor 43, a resistance voltage divider circuit 44 and a reactive-current resistor 45. The capacitor 42 is disposed between the cathode of a photo-diode (PD) 21 and the minus input terminal of the comparator 41. The comparator operation adjustment resistor 43 is disposed between the plus terminal of a primary battery 271 and the minus input terminal of the comparator 41. The resistance voltage divider circuit 44 is constituted by a series connection of voltage dividing resistors 441 and 442. One end of the resistance voltage divider circuit 44 is connected to the plus terminal of the primary battery 271. The junction between the voltage division resistor 441 and the other voltage division resistor 442 is connected to the plus input terminal of the comparator 41.

A data carrier 2 is provided with a comparator 41, a capacitor 42, a comparator operation adjustment resistor 43, a resistance voltage divider circuit 44 and a reactive-current resistor 45. The capacitor 42 is disposed between the cathode of a photo-diode (PD) 21 and the minus input terminal of the comparator 41. The comparator operation adjustment resistor 43 is disposed between the plus terminal of a primary battery 271 and the minus input terminal of the comparator 41. The resistance voltage divider circuit 44 is constituted by a series connection of voltage dividing resistors 441 and 442. One end of the resistance voltage divider circuit 44 is connected to the plus terminal of the primary battery 271. The junction between the voltage division resistor 441 and the other voltage division resistor 442 is connected to the plus input terminal of the comparator 41.

An optical link power management scheme takes the best advantage of a dynamic connection environment, where ports may be connected and disconnected at any time, and where data flows may start and stop as needed by the applications using the high speed data links. Power consumption is optimized, eye safety standards are met, and robust connection detection is preserved.

An optical link power management scheme takes the best advantage of a dynamic connection environment, where ports may be connected and disconnected at any time, and where data flows may start and stop as needed by the applications using the high speed data links. Power consumption is optimized, eye safety standards are met, and robust connection detection is preserved.

A digital optical transmitter of the present invention comprises an optical modulator, pre-equalization factor computation means for generating transform functions for compensating waveform distortion to occur in the optical modulator, and pre-equalization signal generation means for outputting third data and fourth data after creating them by performing a pre-equalization process on first data and second data. Here, through the transform functions, the first data is added to the fourth data, in a manner depending on a characteristic of the optical modulator, and the second data is added to the third data, in a manner depending on a characteristic of the optical modulator.

A digital optical transmitter of the present invention comprises an optical modulator, pre-equalization factor computation means for generating transform functions for compensating waveform distortion to occur in the optical modulator, and pre-equalization signal generation means for outputting third data and fourth data after creating them by performing a pre-equalization process on first data and second data. Here, through the transform functions, the first data is added to the fourth data, in a manner depending on a characteristic of the optical modulator, and the second data is added to the third data, in a manner depending on a characteristic of the optical modulator.

A multi-channel free-space optical wavelength division multiplexing system for optical quantum communication includes a transmitter configured to encode an input signal into a weak optical signal carrying quantum information, and to transmit the weak optical signal over a plurality of frequency channels in free space, each of the plurality of frequency channels corresponding to a plurality of photons of the weak optical signal, and a receiver configured to receive and decode the weak optical signal.

A multi-channel free-space optical wavelength division multiplexing system for optical quantum communication includes a transmitter configured to encode an input signal into a weak optical signal carrying quantum information, and to transmit the weak optical signal over a plurality of frequency channels in free space, each of the plurality of frequency channels corresponding to a plurality of photons of the weak optical signal, and a receiver configured to receive and decode the weak optical signal.

The optical communication apparatus includes a random number generator, a first key manager, a first encryption and decryption device, a driver and a transmitter. The random number generator is configured to generate a random number based on a time frequency. The first key manager is configured to generate a first key based on the random number, store and manage the first key and a second key obtained from an outside. The first encryption and decryption device is configured to encrypt the first key according to the second key to obtain a first encrypted key, and is configured to encrypt initial communication data according to the first key to obtain encrypted data. The driver is configured to obtain the encrypted data and encode the encrypted data into a visible light emission instruction. The first transmitter is configured to receive the visible light emission instruction and emit first visible light.