Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A precise, tunable, low loss add/drop filter for use in fiber optic communication systems utilizes a cascaded system of Mach Zender-like stages, along with reflective elements to return passed channels to the output pass+add signal while transmitted signal(s) appear at the drop port. The optional add signal follows the reverse path of the drop signal and is added to the pass signal.

Abstract: A communication system includes a plurality of nodes and a plurality of point-to-point links that interconnect the plurality of nodes into a network. Each node includes an optical switch to controllably route a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch. Each point-to-point link includes a free space optical channel. A first free space optical channel couples to a first node through a receive path and through a transmit path. The receive path couples to a respective in-port of the optical switch of the first node, and the transmit path couples to a respective out-port of the optical switch of the first node. In an alternative embodiment, a communication hub includes a plurality of neighborhood links to corresponding users, an optical switch coupled to the plurality of neighborhood links, and a trunk coupled between the optical switch and a free space optical channel link to the network.

Abstract: Methods and apparatuses are contemplated for sharing optical sources in an optical network, which typically reduces the number of optical sources needed to operate the optical network.

Abstract: Optical communications networks are provided that allow network maintainers to monitor or control subsystems using communications links other than optical telemetry links. The communications links may be wireless links or may be based on any other suitable communications links such as links using Ethernet cables or telephone lines. Network subsystems may be provided that include communications circuitry for communicating over the communications links. A network maintainer may use network control and management software implemented on computer equipment at a different location than the subsystems to communicate with the subsystems over the communications links. Because the communications links may function independently from the optical telemetry channels in the network, new subsystems may be added to the network without disturbing the existing network management software or telemetry arrangement.

Abstract: This disclosure relates to a laser communication system which allows changing the direction of reception and transmission without external manipulation of the system container. The basic unit of the system is a narrow-band transmitting-receiving telescope apparatus which includes a rotating diffraction grating and an independently rotating stage with mounted combination of photodetector for reception and laser for transmission and a focusing system concentrating the beam reflected from the grating onto the photodetector of the combination or sending a beam from laser of the combination onto the grating. The selection of definite angles for signal transmission-reception is realized by corresponding rotation of grating and rotating stage to the proper angles. The apparatus is intended for spectrally selective transmitting or receiving of optical radiation.

Abstract: There is disclosed a photoelectric conversion method, a light receiving circuit, and an optical communication system, in which even if an average received light level varies, a constant output level of demodulated signal can always be obtained. In the photoelectric conversion method, the light receiving circuit and the optical communication system of the present invention, a light signal is received by a light receiving diode and converted to an electric signal. An alternating component is removed and a direct current component is taken out by a low-pass filter to detect an average received light level of the light, a difference of the average received light level and a preset reference voltage is amplified by a differential amplifier to output a control voltage of a variable gain amplifier, and the electric signal is amplified with a gain corresponding to the control voltage by the variable gain amplifier to obtain a demodulated signal.

Abstract: An arrangement and a method for testing a telecommunications circuit over Dense Wavelength Division Multiplexing (DWDM). A transmitter, which is optically coupled to the circuit, transmits a test-drive signal on the circuit. Through a network, a performance of the circuit is monitored at points along the circuit based on the transmitted test-drive signal.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: The present invention relates to a branch line monitoring system and branch line monitoring method comprising a configuration which improves the S/N ratio of measurement information and can be realized inexpensively. This system is provided with optical filters which correspond to optical fiber lines to be monitored as branch lines. These optical filters each have such a cutoff characteristic as to cut of f respective one channel of monitor light but transmit therethrough the remaining monitor light and signal light. When the optical filters having such a cutoff characteristic are provided, each of the optical fiber lines is monitored by use of a plurality of channels of monitor light other than the one cut off by the optical filter provided so as to correspond thereto. Consequently, as compared with the case where one optical fiber line is monitored by its corresponding one channel of monitor light, the S/N ratio of measurement information is improved, whereby highly accurate monitoring is possible.

Abstract: An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and data payload propagate through network elements with the same path and the associated delays. The technique effects survivability and security of the optical networks by encompassing conventional electronic security with an optical security layer by generating replicated versions of the input data payload at the input node, and the transmission of each of the replicated versions over a corresponding one of the plurality of links. Moreover, each of the links is composed of multiple wavelengths to propagate optical signals or optical packets, and each of the replicated versions of the data payload may be propagated over a selected one of the wavelengths in each corresponding one of the plurality of links.

Abstract: Methods and systems for PMD compensation in an optical communication system are implemented by transmitting multiple optical signals through a common optical conduit to an optical compensator that adjustably rotates the polarization states of the multiple optical signals and transmits the rotated optical signals to an optical receiver. The receiver, upon sensing an excessive error condition, commands the optical compensator to change the polarization state of rotation, which changes the PMD profile of the received optical signals.

Abstract: An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and data payload propagate through network elements with the same path and the associated delays. The technique effects survivability and security of the optical networks by encompassing conventional electronic security with an optical security layer by generating replicated versions of the input data payload at the input node, and the transmission of each of the replicated versions over a corresponding one of the plurality of links. Moreover, each of the links is composed of multiple wavelengths to propagate optical signals or optical packets, and each of the replicated versions of the data payload may be propagated over a selected one of the wavelengths in each corresponding one of the plurality of links.

Abstract: An optical transmission system for an optical communications system that has an optical source, an optical modulator for modulating an optical output of the optical source, and an optical filter arranged to substantially remove one of the upper and lower sidebands of the modulated optical output of the optical source. The optical transmission system further includes a control means to control at least one of the optical source and the optical filter to ensure that substantially only half of the power of the modulated optical output of the optical source is transmitted by the filter, thereby reducing the bandwidth of the optical signals transmitted by the system.

Abstract: The present invention relates to an optical transmission system and a channel assigning method with structure to reduce dispersion of power levels among signals dropped at respective signal branchpoints on an optical transmission line out of signals of multiple channels amplified in an optical amplifier. The optical transmission system has an optical transmission line in which signals of multiple channels propagate, an optical amplifier provided on the transmission line, and a plurality of signal branchpoints disposed on the downstream transmission line in which the signals of the channels outputted from the optical amplifier propagate. Each of the signal branchpoints drops a signal of a channel with a lowest power level out of arriving signals in the channels. This reduces the dispersion of power levels among signals dropped at the respective branchpoints, as a whole of the optical transmission system.

Abstract: This invention discloses a wave division multiplexing communications system including a pluarity of optical transmitters, each of said optical transmitters further including a distributed feed back laser characterized in that it has a dispersion penalty of less than 2 dB when used for transmission into an optical fiber having chromatic dispersion of 1800 ps/nm, a driver operative for receiving a communications signal input and providing electrical power to said distributed feed back laser in accordance therewith and a wave division multiplexer receiving outputs from said plurality of optical transmitters comprising thin film dielectric layers and having a maximum power insertion loss of 4.5 dB.

Abstract: An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and data payload propagate through network elements with the same path and the associated delays. The technique effects survivability and security of the optical networks by encompassing conventional electronic security with an optical security layer by generating replicated versions of the input data payload at the input node, and the transmission of each of the replicated versions over a corresponding one of the plurality of links. Moreover, each of the links is composed of multiple wavelengths to propagate optical signals or optical packets, and each of the replicated versions of the data payload may be propagated over a selected one of the wavelengths in each corresponding one of the plurality of links.

Abstract: The optical transmitter includes a semiconductor laser device, and an optical modulator region optically connected to the semiconductor laser device and having the function of modulating the output light from the semiconductor laser device. The operating temperature of the optical modulator region is changed without changing the oscillation wavelength of the semiconductor laser device.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and data payload propagate through network elements with the same path and the associated delays. The technique effects survivability and security of the optical networks by encompassing conventional electronic security with an optical security layer by generating replicated versions of the input data payload at the input node, and the transmission of each of the replicated versions over a corresponding one of the plurality of links. Moreover, each of the links is composed of multiple wavelengths to propagate optical signals or optical packets, and each of the replicated versions of the data payload may be propagated over a selected one of the wavelengths in each corresponding one of the plurality of links.