Abstract: An optical attenuator includes a first multi-mode waveguide varying a phase of an optical signal input through an input terminal; first and second single-mode waveguides having an input terminal coupled to an output terminal of the first multi-mode waveguide and varying a phase of the optical signal by a thermo-optic effect by electrodes attached thereto; and a second multi-mode waveguide having an input terminal coupled to an output terminal of the first and second single-mode waveguides and varying a phase of the optical signal, wherein a predetermined optical power distribution obtained by offsetting or adding up a phase varied in the first and second multi-mode waveguides and a phase varied by the thermo-optic effect is transferred to an output terminal of the second multi-mode waveguide.

Abstract: A higher order mode generator includes a straight waveguide having upper and lower cladding layers and a core layer which support higher order modes higher than the 0th order. A linear heater is disposed across the waveguide at a tilt angle &agr; with respect to the waveguide. For converting the 0th order optical guiding mode into the mth order optical guiding mode, a tilt angle &agr; of the linear heater and the mth order mode propagation angle &thgr;m satisfy the condition: &agr;>&thgr;m/2.

Abstract: A fiber-attached optical device with in-plane micromachined mirrors includes a cover having at least one reflector formed on one side and a substrate having a plurality of micromachined optical mirrors formed substantially on a single plane on a side facing toward the mirrored side of the cover. The micromachined optical mirrors are controllable to reflect optical signals between a plurality of optical fiber segments via the at least one reflector. The plurality of optical fiber segments can be attached to either the cover or the substrate so as to form an integrated package including the substrate, the cover, and the plurality of optical fiber segments. The mirrors can be controlled to variably attenuate the optical signals.

Abstract: A system and method for automatically attenuating optical signals transmitted in optical systems. The system and method exploits a wavelength-locked loop servo-control circuit and methodology that enables real time mutual alignment of the center wavelength of an optical signal having a peaked spectrum function and transmitted through the optical system, and a center wavelength of a wavelength selective device such as an optical filter element implementing a peaked passband function. The wavelength-locked loop servo-control circuit and methodology particularly is capable of real-time aligning the center wavelength of an optical signal in a range between maximum overlap with the center wavelength of the peaked passband function of the optical filter for maximum transfer of output optical signal by the filter element and minimum overlap with the peaked passband function of the optical filter so that output optical signal may be attenuated in the optical system.

Abstract: A variable optical attenuator includes a base (12), an attenuating means (11), a first collimator (13) retaining an input fiber (18), a second collimator (14) retaining an output fiber (20) and an optical baffle (116). The attenuating means has four anamorphic prisms (111,112,113,114). The optical baffle is driven to move into light path of the first collimator and is expanded by two anamorphic prisms to block a part of the light beam. Thereafter, the retaining part of the light path passes through other two anamorphic prisms and shrinks to form a parallel light beam received by the second collimator.

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: A self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.

Abstract: Disclosed is a path-converted variable optical attenuator comprising: a transmitting fiber for launching an optical signal through a transmitting core; a receiving fiber for receiving the optical signal from the transmitting fiber through a receiving core; and a mirror having a reflector for obstructing the optical signal launched from the transmitting core of the transmitting fiber from proceeding into the receiving core of the receiving fiber, and being displaced in a direction allowing a portion of the optical signal of the transmitting fiber into the receiving fiber to attenuate the optical signal. An optical signal launched from the transmitting fiber to the receiving fiber is reflected to a separate path from paths of transmitting/receiving fibers so that attenuation may not vary according to wavelength.

Abstract: An optical device comprises a waveguide assembly having a number of core portions along which radiation can propagate from an input port to an output port and cladding portions abutting said core portions. Each core portion is adapted to receive a beam composed of a respective wavelength band of radiation. The device also comprises a demultiplexer for separating a signal comprising a plurality of channels into separate channel beams for input into the waveguide and/or a multiplexer fro receiving the beams from the waveguide and recombining them into a single signal. Preferably, the waveguide incorporates optical attenuation means operative on the beams. In one embodiment, the core portions and/or abutting cladding portions are comprised of a polymer-dispersed liquid crystal material whose refractive index can be varied by the application of an electrical stimulus.

Abstract: A variable optical attenuator comprising a lightguide defining an optical path, the lightguide being divided into first (1) and second parts (2) separated by a gap (3) which crosses the optical path; an optically transparent actuator (7) adapted to be displaced within the gap along a path inclined to the optical path to attenuate a light beam passing along the optical path; the actuator having front (8) and rear (9) faces, at least a portion of the rear face (9) being inclined to the optical path such that the light beam incident on the rear face is substantially totally internally reflected by the rear face within the actuator.

Abstract: A variable optical attenuator has a first movable waveguide support and a second waveguide support that include first and second waveguides, respectively, such that the first and second waveguides are aligned for propagating an optical energy. An electrically driven actuator positions the movable waveguide support for coupled, optical misalignment relative to the second support to achieve a desired optical attenuation value. The movable waveguide support may be in a cantilevered configuration in which a distal end extends over a surface having an electrode. In this example, applying a drive signal to the electrode deflects the movable support such that the signal coupled between the first waveguide to the second waveguide is attenuated. The drive signal may be set to achieve a desired value for an electrical parameter that varies with the position of the movable waveguide support.

Abstract: An optical device and system and method for monitoring a fault condition in an optical device. A loop-back path couples a portion of an optical signal from a first transmission path to a second transmission path as a loop-back signal. The loop-back path includes at least one optical attenuator configured to attenuate the loop-back signal in response to at least one detected condition. The loop-back signal may be detected by line monitoring equipment, where the attenuation imparted by the attenuator is interpreted as corresponding to the detected condition.

Abstract: A mechanically-adjustable variable optical attenuator includes an azimuthally-tapering, rotatable beam attenuator. In a plane perpendicular to the light beam to be attenuated, the projection of the beam attenuator comprises a sharp distal tip, a proximal region, and a concave curved light-blocking surface narrowing from the proximal region to the distal tip. The extent of the beam attenuator obstructing the light beam is varied by rotating the beam attenuator about a rotation axis perpendicular to the light beam direction. The beam attenuator geometry allows achieving high resolutions while limiting the beam attenuator size. The attenuated light beam can be a single-mode or multi-mode light beam.

Abstract: In the manufacture of an optical attenuator having a desired value of the optical loss end regions of two optical fibers are placed with an offset in the traverse direction in relation to each other and having their end surface at each other. Thereafter the region at end surfaces is heated to make the ends melt to each other and the heating is then further continued. To achieve the desired loss in the finished attenuating splice the further heating is stopped for an optical loss exceeding the desired loss by a calculated value. This value can be obtained from measurements in real time of the loss for the splice during the continued heating. The measurements can be made at the beginning and end of an interrupt of the further heating. An attenuator manufactured in this way obtains an attenuation that accurately aggres with the desired value.

Abstract: Methods and apparatus are provided for the closed loop attenuation of optical beam power in a multiple-axis free-space-coupled single-mode fiber-optic transmission system. In a specific embodiment involving two tip-tilt mirrors to couple optical power from an input fiber to an output fiber, the four mirror axes arc actuated in such a way as to produce either a static or time-varying set of induced mirror angles that yield a desired time history of optical loss. The attenuation technique uses the DC level of the measured output power to adjust the amplitude of the induced mirror angles.

Abstract: A method and system for adjusting power at output ports of a wavelength division multiplexing (WDM) coupler. A loss element may be placed at one or more of the output ports of the WDM coupler. The loss element may have a filter characteristic that matches the temperature sensitivity coefficient of the WDM coupler. The filter characteristic may reject power at one of the two output ports as a function of temperature. As a result, the loss element may balance the power at the output ports of the WDM coupler despite temperature variations.

Abstract: An optical loop-back attenuator (2) includes a frame (22), a cover (21) attached to the frame, an optical fiber (24), an optical fiber fixture (23) retaining and fixing the optical fiber, and two SC plug connectors (25) receiving and retaining opposite ends of the optical fiber therein. The frame and the cover cooperate to fittingly receive the optical fiber, the optical fiber fixture and portions of the SC plug connectors therein. The optical fiber has a bent part (242) which is configured to be semicircular or to have another suitable shape that achieves a desired attenuation.

Abstract: A concept of designing a Variable Optical Attenuation Collimator (VOAC) is disclosed to achieve a variable degree of optical power attenuation through the collimator by adding an Attenuation Control Element (ACE) between a lens element and fiber pigtails of a traditional fiber optical collimator. The body of the ACE can be implemented in many different forms of a light blocker element capable of being controllably moved into a main light path of the VOAC to obstruct a controlled portion of light power. The light blocker can be a Micro Electro Mechanical Structure (MEMS) operating with a controlled electrostatic force, a bimetal wire driven by a controlled heating current, an electrical current-carrying wire within a surrounding permanent magnetic field or a deflectable permanent magnetic wire within a controlled surrounding magnetic field.

Abstract: A variable attenuation device for optical signal transmission has first and second ferrules or plugs having abutting end faces, one of the ferrules being rotatable with respect to the other while axial alignment therebetween is maintained. Each ferrule or plug has an axial bore aligned with the other and contains the end of an optical fiber, with a fiber having a smaller diameter than the diameter of the bore in which it is contained so that the fibers may have decreased engagement with each other when there is relative rotation of the ferrules although the ferrule bores remain aligned.

Abstract: Disclosed is a thermo-optic (TO) switch that reduces the difficulty in the fabrication process and has an excellent optical crosstalk. In the TO switch, variable optical attenuators utilizing higher-order mode generators are integrated to the both output ports of a conventional 1×2 digital TO switch of Y-branch type waveguide which uses mode evolution effect. Even when the Y-branch angle gets bigger, the inventive TO switch can maintain an excellent crosstalk without raising the switching power. Since a large Y-branch angle can reduce the difficulty in fabrication process, the inventive TO switch will increase the production rate. 1×2 optical switch is an essential device in an optical signal processing system such as optical communications, optical switches and optical sensors.

Abstract: A waveguide type variable optical attenuator has: a substrate; two optical circuits that are in parallel formed on the substrate, each of the optical circuits including two couplers that conduct the branching and coupling of light and are connected to the input port and output port of light and two waveguides through which the two couplers are connected; a polarization maintaining fiber one end of which is connected to the output port of one of the two optical circuits and the other end of which is connected to the input port of the other of the two optical circuits while being twisted 90°; and a heater that is provided around neighboring waveguides of the two optical circuits such that the neighboring waveguides share heat to be generated by the heater.

Abstract: A variable attenuator has first and second substantially identical ferrules or capillaries, each being mounted in a barrel or splice housing and extending toward each other, with their distal ends being separated by a gap of a first width. The width of the gap is controlled by a sleeve into which the ferrules are inserted, the ends of the sleeve butting against the front faces of the barrels. The ferrules are made by producing a glass rod mounted between the barrels and having a bore offset from and parallel to the centerline of the rod and breaking or cleaving the rod at its longitudinal center. The broken ends are then polished. The barrels are keyed to a housing member so that the offset bores are coincident in the zero position as defined by the keys.

Abstract: A technique for manufacturing optical fixed attenuators in which two fibers are axially cojoined using fusion splicing. The spliced fibers are then captured in either a splice protection splint or cylindrical ferrule that can be housed in an optical adapter. In this process for producing the attenuator, the fusion splicing is preceded by a deformation of the mode field diameters of the ends of the fibers with the cleaning arc function of the splicing unit. The resulting attenuation of the splice is dependent on the amount of deformation of the fiber core and mode field diameter. Such a technique enables precision attenuation with very low wavelength dependent loss to be fabricated. The performance of Dense Wavelength Division Multiplexing systems, as well as test facilities and individual optical components can be improved by the use of such attenuators.

Abstract: In an amplified wavelength division multiplexes (WDM) fiber optic communication system, each channel experiences a different optical gain, dispersion and noise. Also, the evolution of WDM fiber optic systems to higher density channel spacing has further aggravated multi-channel non-linear distortions such as four-wave mixing (FWM) and cross-phase modulation (XPM). The standard method for controlling these nonlinearities is the peak power control method. The performance of the channels can be equalized by adjusting the transmission powers of the optical transmitters. However, just equalization of a performance indication factor (PIF) such as BER or Q is not the optimum approach when peak power control mode of operation dominates. This invention is directed towards improving the margins of performance of WDM fiber optic channels.

Abstract: An optoelectronic module includes a variable optical attenuator with further passive and active optical components to form an integrated module, which is inexpensive and yields small yet robust packages. The module provides for a variable output power and can be installed and replaced via a ‘hot pluggable’ connector.

Abstract: An optical signal processing apparatus based on movable tilted reflection mirror comprises a movable tilted reflection mirror unit and a micro actuator. The micro actuator is used to control and actuate the relative location and position of the movable reflection mirror unit with respect to the optical transmission path of light signals. To control the light intensity of the incoming optical signals being reflected toward output ports and the light intensity of the optical signals transmitted forward to output ports, the light intensity is adjusted in terms of the location of the movable tilted reflection mirror unit which is determined by electrically controlling said micro-actuator. The movable tilted reflection mirror unit comprises at least one reflective mirror plane, which can be a flat mirror plane, a shaped mirror plane, or a curved mirror plane.

Abstract: A Variable Optical Attenuation Collimator (VOAC) is disclosed to achieve a variable degree of optical power attenuation through the collimator by adding an Attenuation Control Element (ACE) between a lens element and fiber pigtails of a traditional fiber optical collimator. The body of the ACE can be implemented in many different ways such as a polymer-network liquid crystal light scattering and absorbing material, a Refraction Index Gradient Controllable Material (RIGCM) capable of controllably swerving the direction of light propagation, a Refraction Index Controllable Material (RICM) capable of controllably defocusing an incident light power and a transparent Length Controllable Material (LCM) capable of controllably changing the spacing between the lens element and the fiber pigtails causing a defocusing of an incident light power.

Abstract: A method for equalizing optical signal power in a group of optical signals transmitted through an optical switch in an optical transmission system. In one embodiment a group of optical signals is input into an optical switch having at least one movable mirror array with a plurality of reflectors formed thereon, the optical beam being directed onto a selected at least one reflector and wherein attenuating the optical beam is accomplished by controllably detuning at least one of the selected at least one reflector to attenuate the optical beam.

Abstract: In a light attenuator or its attenuating method, a nonlinear optical material and an aperture section are placed respectively on a same optical axis, between a receiving optical fiber and a sending optical fiber. The nonlinear optical material receives and refracts an input light outputted from the receiving optical fiber. The aperture section has an aperture, receives the light having passed through the nonlinear optical material, and outputs constant output light to the sending optical fiber by only allowing a part of the light to be outputted from the aperture. Then, for obtaining the wishful output light with constant strength no depending upon the input light, these parameters of the quadratic nonlinear refractive index n2 and the thickness t of the nonlinear optical material; the distance L between nonlinear optical material and aperture section; and the diameter Ø of the aperture, are set most appropriately.

Abstract: An attenuating device for attenuating optical power of a light beam, comprises an at least partly absorbing element adapted to receive and attenuate the optical power of the light beam, and a supporting element for supporting on at least one side the at least partly absorbing element. The at least partly absorbing element comprises at least one layer coated or evaporated on the supporting element with an increasing, decreasing, or varying thickness. The supporting element is provided with a material having a crystalline structure to provide compensation to a local heating in the at least partly absorbing element resulting from absorption of the light beam.

Abstract: Micro electro-mechanical devices, which may be formed using deep etching, and which comprise a vertical micro-mirror 14 coupled to an actuation mechanism for tilting the mirror, preferably about the vertical axis are disclosed. The mirror 14 and actuation mechanism are formed on the same substrate and thus form an integral device or chip.

Abstract: A manual variable optical attenuator (10) includes a base (2), a cover (3), an optical module (4), a shifting device (5), and an optical fiber retainer (6). The optical module comprises a mirror (41), a frame (42), a dual optical fiber collimator (43), a stopper (44), a graded transmittance filter (45), and a filter carrier (46). The shifting device comprises a screw pole (51), a first holder (52), and a second holder (53). The screw pole comprises a terminal portion (511) rotatably received in the first holder, a first annular groove (512) accommodating the second holder, a second annular groove (513) receiving a gasket (514), an adjusting slot (515), and a screw thread (516). The gasket protrudes from a circumferential surface of the screw pole and seals a gap between the screw pole and a sidewall (36) of the cover. External harmful contamination cannot penetrate into the attenuator.

Abstract: Provided are an optical rotator which is capable of switch-operating at high speed, small in size and low in price, an optical switch readily compatible with an array structure and matrix form, and a variable optical attenuator readily compatible with an array structure. In the present invention, an optical rotator 14 comprises a lamination coil 10a, . . . , 10c having a through-hole and a Faraday element 11 arranged in the through-hole or a vicinity thereof, whereby a magnetic field caused by the coil is applied to the Faraday element. The Faraday element is arranged such that light passes vertically to the main surface thereof in which direction a magnetic field can be applied. A magnetism-holding member of a high magnetic permeable material is preferably arranged at least in a part of an outer periphery of the coil. In case the Faraday element uses a magnetic garnet crystal having a residual magnetization, obtained is an optical rotator having a self-sustaining function.

Abstract: Control systems and methods are provided for controlling optical energy transmitted through a fiber optic. The systems and methods employ a digital controller circuit coupled to at least one sensor for receiving a sensed level stimulus output therefrom, and coupled to a fiber optic power control device for providing a digitized feedback signal thereto. The digital controller circuit, which can operate in one of a plurality of modes and automatically switch between modes, can include one or more of a digital filter, memory for storing control programs and data, an analog-to-digital converter for converting received sensed level stimulus to a digital signal, a digital communication interface, and a processor for software processing of the digital signal. Automatically powering up or resetting the digital power control system is also provided.

Abstract: This invention relates to a sled-guide-assembly (1), in particular for an optical attenuating device, comprising a straight guidance (2) and a sled (3), which is movable within the guidance (2), wherein

Abstract: A current tuned optical attenuator includes a Mach-Zehnder interferometer that relies on the creation of free carriers to create a phase difference in an optical signals along two waveguide arms.

Abstract: An optical module has a planar waveguide which is provided with an optical circuit for an optical switch formed by 2×2 cross optical waveguides A1 to D1 and an optical circuit for an optical variable attenuator formed by 2×2 cross optical waveguides A2 to D2. Joined onto the planar waveguide is an actuator structure and the actuator structure is constituted by an actuator section for an optical switch and an actuator section for an optical variable attenuator. The optical circuit of the planar waveguide and the actuator section constitute an optical switch, whereas the optical circuit of the planar waveguide 2 and the actuator section constitute an optical variable attenuator.

Abstract: A method and apparatus for a VOA with improved wavelength-dependent optical losses is provided. The primary elements of this improved VOA are a package, a movable structure with a reflecting surface, and a collimator. The collimator is comprised of various optical components including a ferrule holding at least two waveguides and a lens. Selecting a ferrule and a lens such that the plane containing the end of the ferrule and the ends of the waveguides is not parallel to the facing end of the lens, it is possible to determine positions and axial orientations of the ferrule with respect to the lens which result in minimal wavelength-dependent optical losses. By geometrically configuring the optical components of the collimator in this way, and subsequently positioning and axially orienting the collimator and movable structure to minimize wavelength-dependent losses, a VOA with minimal wavelength-dependent optical losses can be constructed.

Abstract: An optical variable attenuator has a planar waveguide, which is provided with optical waveguides forming an input optical line A and an output optical line B. A cantilever is disposed at the upper face of the planar waveguide, whereas a movable mirror for reflecting light passing through the input optical line A toward the output optical line B is secured to the leading end part of the cantilever. An electrode is disposed at the upper face of the planar waveguide. The cantilever and the electrode are connected to each other by way of a voltage source. The voltage source applies a voltage between the cantilever and the electrode, so as to generate an electrostatic force therebetween, which flexes the leading end side of the cantilever toward the electrode. As a consequence, the movable mirror moves toward the electrode.

Abstract: A controllable attenuator includes a pair of collimators respectively connected to input and output fibers. A pair of reflection devices are respectively positioned behind the pair of collimators opposite to the corresponding input and output fibers. A U-like light path is defined among the pair of collimators and the pair of reflection devices. A neutral density filter is moveably positioned between the pair of reflection devices wherein a moving direction of the filter is preferably parallel to a longitudinal direction of the pair of collimators. An ND filter position indicator such as a potentiometer, is used to dynamically monitor attenuation setting.

Abstract: An optical attenuator having a multi-mode waveguide segment and a perturbation element. An incident single-mode optical signal is converted to a multi-mode optical signal in the multi-mode waveguide segment. The optical attenuator couples incident light into higher order modes of the multi-mode waveguide segment resulting in attenuation of the incident optical signal.

Abstract: A multi-fiber in-line attenuator module configured for insertion in the fiber optic pathway of an optoelectronic network to provide a predetermined value of attenuation for all propagating modes in the pathway includes first and second multi-channel interface members each having a mating face, an interconnect face, and alignment holes and n-optical channels formed therethrough, a multi-fiber ribbon cable terminating in the interconnect face of each multi-channel interface member with the optical fibers thereof disposed in the n-optical channels, alignment pins disposed in the alignment holes of the first and second multi-channel interface members so that the n-optical channels of the first and second multi-channel interface members are optically aligned, a mating clip for retaining the first and second multi-channel interface members in mated combination, and an NDF (neutral density filter) film adhered to at least one of the mating faces of the first and second the multi-channel interface members, the adhere

Abstract: The invention explains, inter alia, integrated waveguide arrangements in which a waveguide with glass core and glass sheath is arranged in a waveguide layer consisting of glass. A foreign region made from a material other than glass extends in the vicinity of the waveguide. A temperature-adjustment unit is used to heat and/or cool the foreign region. The foreign region is integrated in the waveguide region.

Abstract: An optical function module comprises a collimator block having a substrate, at least two collimators disposed on the substrate in confronting relation to one another for collimating a light flux directed along a preselected path between the collimators, and support members each for supporting a respective one of the collimators on the substrate. An optical function device is removably connected by a connecting structure to the collimator block so that the optical function device is positioned along the preselected path of the light flux between the collimators.

Abstract: An optical filter has a first long-period grating and a second long-period grating formed in a unitary optical fiber. A difference is not less than 100 nm between a wavelength at which optical coupling is maximum between core-mode light and cladding-mode light of a predetermined mode number in the first long-period grating and a wavelength at which optical coupling is maximum between core-mode light and cladding-mode light of the same mode number as the cladding-mode light of the predetermined mode number, in the second long-period grating. This optical filter can be constructed in compact size and can readily implement a desired transmission characteristic.

Abstract: A variable optical attenuator (10) of the present invention includes a cover (2), a housing (3), an optical module (4), a reciprocating means (5), and a filter (9). The reciprocating means, optical module, and filter are assembled in the housing. The reciprocating means includes a carrier (53) mounted to a rotatable screw rod (55). The filter has a varying optical density gradient over one of its dimensions and mounts on the carrier. Light signals are transmitted from an input optical fiber (45) through the filter and are reflected off a reflector (42) of the optical module to pass again through the filter to an output optical fiber (46). When the screw rod is rotated, the carrier with the filter mounted on it moves toward one side of the housing or another, varying the attenuation of the light signals. The screw rod can be rotated using a screwdriver through a side hole (33,34) on either side of the housing.

Abstract: A method and apparatus for controlling the attenuation level of a semiconductor VOA relative to an absolute temperature of the VOA without the use of a power monitor is provided. The method includes the step of providing a variable optical attenuator for attenuating the optical signal. The variable optical attenuator is instructed to maintain the desired attenuation level of the optical signal. The temperature of the variable optical attenuator is periodically sensed, and a required voltage level is determined to achieve the desired attenuation level based at least partially on the periodically sensed temperature of the VOA. The method can further include the step of increasing and decreasing a voltage to the VOA to achieve the required voltage level and thus the desired attenuation level.

Abstract: One aspect is a method for controllably attenuating the beam of light (108) coupled between incoming and outgoing optical fibers (106) by misaligning minor surfaces (116a, 116b) included of an optical switching module (100). Misalignment of the mirror surfaces (116a and 116b) causes only a portion of the beam of light (108) propagating along the incoming optical fiber (106), which is less than when the light beam deflectors' mirror surfaces (116) are precisely aligned, to propagate along the outgoing optical fiber (108). Thus, the optical switching module (100) controllably attenuates the beam of light (108) coupled between the incoming and the outgoing optical fibers (106). Another aspect is a variable-optical-attenuator (“VOA”) (212) that includes an optically reflective membrane (222) upon which the beam of light (108) impinges.

Abstract: In an optical signal level control apparatus used in a WDM system, the amount of circuitry per wavelength is reduced. Optical power level is detected on the output side of a variable optical attenuator, and the amount of attenuation in the variable optical attenuator is adjusted so that the output level becomes equal to a constant value L1. At this time, if the detected level is lower than a threshold value Th0 or Th-d, it is determined that a signal off condition has occurred, and the amount of attenuation is set to a constant value A1. The amount of attenuation, A1, is chosen to be sufficiently larger than the amount of attenuation used in the output level constant control but small enough to be able to detect the restoration of the signal. When the amount of attenuation is being held at the constant value A1, if the output level is restored to a level higher than the threshold value Th0 or Th1 (Th1<Th-d), the output constant control is resumed.

Abstract: An optical coupling assembly having an optical receiver that exhibits extended dynamic range, and, more particularly, an optical receiver that is integrated with a Variable Optical Attenuator (VOA) to extend the dynamic range of the receiver.