Abstract: The present invention provides a method for transmitting terminal connection control signals and supervisory signals between a photonic switching system and its subscriber terminals without using any light source in the photonic switching system. After modulating amplitude of the photonic communications signals by the terminal connection control signals in the form of electric signals the photonic communications signals are inputted to the subscriber terminals to be demodulated for regenerating the terminal connection control signals.

Abstract: An apparatus and a method for performing hitless switching between optical transmission lines such as optical fiber circuits are provided. An optical switch or optical switching network having input terminals and output terminals for selecting optical signals inputted to the input terminals to the output terminals with a selection ratio which can be varied continuously is used. An optical signal converter for generating an optical signal of light which does not interfere with another optical signal is attached to the optical switch. Further, a signal loop interconnecting one of the output terminals of the switch and the input of the optical signal converter is provided.

Abstract: A method and an apparatus for bidirectional optical transmission capable of bidirectional communication through a single optical transmission path are disclosed. A light traveling in one direction is modulated by a first base band signal and another light beam traveling in a second direction is modulated by a subcarrier signal which is modulated by a second base band signal for subsequent conversion into the binary digit pulse. A light receiving circuit for receiving the light traveling in said second direction is comprised of a synchronizing detection demodulator and at least a light receiver to which an electrical signal synchronizing to the subcarrier signal is applied.

Abstract: In an optical packet switching system, a plurality of first wavelength tunable devices are connected respectively to incoming line terminals. In response to an incoming signal at the associated incoming line terminal, each of the first wavelength tunable devices generates an optical packet of a particular wavelength determined by a first wavelength selection signal supplied from a controller. In one embodiment, packets from the first wavelength tunable devices are switched through one or more paths set up by an optical space division switch to one of a plurality of optical buffers. Second wavelength tunable devices are respectively coupled to the outputs of the optical buffers for detecting a packet of a desired wavelength in response to a second wavelength selection signal from the controller and applying the detected packet to one of outgoing line terminals.

Abstract: A time and wavelength (T.times.W) switch comprises a plurality of wavelength selectors for selecting a time division multiplexed (TDM) channel of a first wavelength from a plurality of incoming TDM channels of different wavelengths. A plurality of time-slot switches are connected respectively to the outputs of the wavelength selectors for switching a first time slot of the selected TDM channel to a second time slot. To the outputs of the time-slot switches a plurality of wavelength converters are respectively connected for converting the wavelength of the second time slot to a second wavelength. The T.times.W switches can be arranged as an incoming time and wavelength switching stage and an outgoing time and wavelength switching stage. An array of optical devices interconnecting the outputs of the incoming and outgoing stages constitutes an intermediate stage.

Abstract: An optical wavelength-division multiplex transmission system having an optical filter (100) for filtering spontaneous emission noise from an optically multiplexed signal which has been amplified by an optical amplifier (622), which can be a laser amplifier or a fiber Raman amplifier. The output signal from the optical filter may be further amplified by a second optical amplifier (624), and the second amplified signal may be sent to a further optical filter. The optical filter includes an optical demultiplexer and an optical multiplexer, and can be a Fabry-Perot interferometer or a Mach-Zehnder interferometer. The optical filter is for transmitting pass-bands with center wavelengths corresponding to those of the wavelengths of the optical signals to be transmitted by the optical wavelength-division wavelength multiplex transmission system.

Abstract: A wavelength division optical switching system comprises a plurality of terminals each generating a light signal on a particular wavelength division multiplexed channel and an optical multiplexer connected to the terminals for multiplexing the light signals from the terminals. A processor identifies the channel of a source terminal requesting a connection and the channel of a destination terminal. A reference light generator generates a plurality of reference lightwaves of different wavelengths. A wavelength switch is provided for switching multiplexed channels by selecting the light signal of the identified source terminal channel and modulating the intensity of one of the reference lightwaves with the selected light signal so that the identified channel of the source terminal is switched to the identified channel of the destination terminal.

Abstract: An optical matrix switch comprises 1.times.M/2 optical switch means of N in number, optical switch groups of N/2 in number, and N/2.times.1 optical switch means of M in number, where N is a number of inputs, and M is a number of outputs. Each of the 1.times.M/2 optical switch means includes a predetermined number of optical switch elements each having a function to switch an optical signal between inputs and outputs in accordance with an applied electric field, and has one input and outputs of M/2 in number. The predetermined number is decided dependent on an equation of log.sub.2 M/2. Each of the optical switch groups includes optical switch elements of M/2 in number arranged transversely, and each of the N/2.times.1 optical switch means includes a predetermined number of optical switch elements. The predetermined number is decided dependent on an equation of log.sub.2 N/2. A longitudinal length of the optical matrix switch is approximately (log.sub.2 M/2+1+log.sub.

Abstract: An opto-electric logic element comprises a semiconductor laser having a differential gain characteristic or an optical bistable characteristic and supplied with at least one light input, and a control circuit for varying an injection current supplied to the semiconductor laser in accordance with an input electrical signal. The logic element is capable of executing a logical operation between the optical signal and the electrical signal and can output the results of the logical operation as an optical signal.