Abstract: An adjustable diffractive light modulator is used to equalize the power level of wavelength multiplexed signals in wavelength division multiplexing applications. An optical channel transmits a multi-wavelength input signal through a wavelength demultiplexer. The input signal comprises a plurality of component signals defined according to a plurality of wavelengths. The de-multiplexer spatially separates the multi-wavelength input signal into its respective plurality of component signals, which are transmitted through a plurality of optical channels onto a plurality of controllable diffractive light modulators. The diffractive light modulators are advantageously comprised of grating light valves. Component signals are reflected off their respective diffractive light modulators and collected in a plurality of optical channels for re-transmission into a wavelength multiplexer. The reflected signals are combined through a multiplexing process and transmitted as an output beam.

Abstract: It is described a WDM optical communication method based on the use of a plurality of wavelength specific channels defining a spectrum for the transmission of optical signals through an optical communication network. These optical signals will be coupled at a sender side into a common optical fiber of said network, to be amplified by optical amplifiers along said network. The power of optical signals per channel will be tuned at said sender side to build an uniform—flat—spectrum throughout said optical communication network.

Abstract: An optical packet tray router is disclosed that manipulates a signal wavelength as the fundamental control mechanism. The disclosed optical packet tray router aggregates one or more packets in a packet tray for transmission over a network. The header information associated with each packet is used to route each packet to the appropriate destination channel and to make timing decisions. A wavelength server generates optical control wavelengths in response to the timing decisions. A generated optical control wavelength is used to adjust the wavelength of a given packet tray and thereby introduce a wavelength selective delay to the packet tray to align packet trays or to shift one or more packet trays to avoid a collision. The wavelength of the packet tray is converted to a control wavelength corresponding to an identified delay, irrespective of the initial channel upon which the packet tray was received.

Abstract: A multichannel WDM transmission system incorporates a plurality of WDM optical sources with stabilized wavelengths and light intensity. Efficient stabilization of these characteristics is achieved by modulation of WDM sources by distinguishing low frequency electrical signals in a range between 1 and 4 kHz and modulation depth in a range between 1% and 5% that are used as WDM source identifiers. After the modulated outputs of the WDM sources are multiplexed and filtered, a Fourier transform of total light intensity may be obtained. Digital feedbacks provide stabilization of both the wavelength and light intensity of each WDM optical source.

Abstract: An optical communication system includes a plurality of optical channels, each of which passes a single optical wavelength signal. Each of the plurality of optical channels includes an optical amplifier which is controlled to operate at a predetermined output power level independent of channel wavelength and input power level by operating each optical amplifier in a saturation mode. Pumping power for operating each optical amplifier in the saturation mode is supplied from shared optical pumps or a plurality of one per channel optical pumps.

Abstract: When a branching unit combines a first optical signal transmitted from a branch station with a second optical signal which is different in power level from the first optical signal and is transmitted from a terminal station A or B in an optical add-drop system, the S/N ratio of the lower power level of the two different power levels decreases, thereby deteriorating the system performance. Therefore, a dummy light is transmitted together with an optical signal to adjust the power level of the optical signal. Otherwise, an optical attenuator or an active optical signal level adjustment unit is provided for the branching unit so that both optical signals to be combined can be equal in level.

Abstract: An electro-optic device for use in wavelength division multiplexed systems. The device comprises a layer structure having two adjustable air gaps. Optical response of the device can be changed by adjusting spacings of the air gaps. The device can be used as an optical power equalizer in wavelength division multiplexed systems.

Abstract: There is proposed a method and a module for real time control of power per optical channel in a multi-channel optical communication line formed by a group of optical elements connected in a chain by fiber spans. The group of elements comprises one or more optical fiber amplifiers (OFA); each of the spans is characterized by its span loss, while each of the OFA is characterized by its gain and its designed output power per channel. The method comprises steps of calculating an expected total input power value (EIP) for a particular optical amplifier (OFA) in the line, measuring a real total input power (MIP) at the particular optical amplifier, and comparing the values. If a difference between the EIP and the MIP at the OFA exceeds a predetermined value, the method (and the module) ensures adjusting the gain of the OFA to maintain its output power per channel constant.

Abstract: A power control arrangement for an optical transmission system involves detecting optical power upstream of a delay element, adjusting a perchannel optical power in the optical path downstream of the delay element to maintain the optical power constant. Such a feed forward arrangement enables power transients to be detected in time for pre-emptive control to suppress transients which are too fast to be suppressed otherwise by conventional control of optical amplifiers. This enables a reduction in power margins, and prevents damage to sensitive receivers for example. Such controllers can be distributed through networks and provided at interfaces with other optical networks to enable third party wavelengths to be carried with less risk of damaging transients propagating through the network.

Abstract: Optical signal power levels for selected optical channels processed within an add/drop node in a wavelength division multiplexed (WDM) system are adjusted as a function of variations in signal power in an incoming WDM signal caused by gain ripple. In particular, a “ripple fitting” method is described whereby the optical signal power of individual optical channels being added at the add/drop node are adjusted to levels that correspond to the ripple profile of other optical channels being routed through the add/drop node. In this manner, the gain ripple in the WDM signal being output from the add/drop node approximately corresponds to the gain ripple in the incoming WDM signal at the node.

Abstract: An optical signal repeater, in which an output level of each optical signal of WDM optical signals does not change even when the number of wavelengths of inputted WDM optical signals changes, amplifies WDM optical signals transmitted from an optical transmitter via an optical fiber transmission line. A pumping light source outputs pumping light used for amplifying the WDM optical signal. A multiplexer transmits the pumping light to an amplifier, and a splits the amplified WDM optical signals into two parts. A wavelength selection type reflector reflects only an optical signal having a specified wavelength in one part of the amplified WDM optical signals. An automatic output level controller controls the pumping light output from the pumping light source so that the power level becomes a designated level. A reflected optical signal transmitter transmits the optical signal having the specified wavelength reflected to the automatic output level controller.

Abstract: A bidirectional optical amplifying apparatus-and method of controlling the optical gain in a bidirectional WDM optical communication network includes a bidirectional optical amplifier for amplifying a forward WDM optical input signal and a reverse WDM optical input signal, a measurement means for measuring the total input intensity and the total output intensity of the bidirectional optical amplifier,and a control means for measuring a gain using the total input intensity and the total output intensity, compensating the error between the measured gain and a reference gain, and feedback controlling the bidirectional optical amplifier to uniformly maintain the gain. The measurement means divides a forward optical input signal and a reverse optical input signal, in a constant ratio, respectively, converts the divided optical signal to an electrical signal, and measures total input intensity.

Abstract: A power controlling network element (10) for a communication system, is characterised in that it includes: (a) a detector (30) for measuring radiation power present in components of radiation; (b) element parts, for example a channel control unit (CCU) (60), transponders (90, 92, 94) and other modules, for at least one of: (i) transmitting to the detector (30) at least some components of input radiation received at the elements parts from the system; and (ii) generating one or more components of radiation and emitting said one or more components to the detector (30); (c) a field programmable gate array (FPGA) (40) for receiving data from the detector (30) indicative of radiation power in the components of radiation received at the detector (30), and for controlling radiation power emitted from or transmitted through the aforementioned element parts (60, 70, 80,90, 92, 94), so that the components of radiation received at the detector (30) are regulated in power to within predetermined power limits.