Showing papers on "Optical switch published in 1991"

Optical switch, multiplexer, and demultiplexer

Abstract: An N×N integrated optical interconnection apparatus capable of switching, multiplexing, or demultiplexing a large number of input and output wavelength channels achieves low levels of crosstalk and insertion loss. Two substantially identical N×M star couplers are connected by an optical diffraction grating comprising M unequal length waveguides spaced from one another by predetermined amounts. Each coupler comprises a dielectric slab defining a free space region between two periodic arrays of waveguides, each radially directed toward a virtual focal point. The arrays are configured so that their respective foci are located at a predetermined distance away from and outside the free space region to minimize phase errors caused by mutual coupling between adjacent waveguides. Specifically, the focal point of each array connected to each star coupler may be located so that it coincides with the phase center of the other array connected to each coupler. Residual phase errors may be reduced by appropriately setting the lengths of the waveguides in the optical grating between the two star couplers. The length difference between any two adjacent waveguides in the grating is not constant throughout the grating.

Oxide glasses for fast photonic switching : a comparative study

Abstract: New developments involving nonlinear optical effects are conditioned by the improvement of pertinent figures of merit involving the characteristics of nonlinear optical materials within the ‘‘transparency’’ regime of their optic windows. This paper discusses, from a global standpoint, the maximum values of nonlinear refractive index n2, and of its ratio n2/α relative to intrinsic attenuation α, attainable for a multicomponent oxide glass. It also locates and analyses those classes of multicomponent oxide glass that, from the standpoint of these two measures, appear to be the most promising candidates for use as fast photonic switching elements in the 1–2.5‐μm wavelength regime.

Optical clock distribution using a mode-locked semiconductor laser diode system

Abstract: An experiment in which a high-power mode-locked femtosecond semiconductor laser system was used as a source of extremely low jitter intense optical pulses in the distribution of a clock to 1024 ports via optical fibers is described. The total accumulated dynamic clock jitter between any two ports, which contains both correlated and uncorrelated sources, was measured to be less than 12 ps. This laser system produced a train of 460-fs optical pulses with over 70 W of peak power at 302 MHz. These results represent the largest fanout with the minimum timing jitter for an optically distributed clocking network. >

Integrated optic devices based on nonlinear optical polymers

Abstract: An examination is made of the state of the art of nonlinear optical polymeric materials in view of their potential advantages. It is shown that these organic materials have many attractive features compared to LiNbO/sub 3/ and III-V semiconductors with regard to their use in integrated optic circuits, especially since the level of integration is ever increasing. Considering more specifically electro-optic devices, a description is given of some of the theoretical background and basic properties. These polymers have already demonstrated a very high and extremely fast electro-optic effect compared to LiNbO/sub 3/. It is also shown how low-loss waveguides can be fabricated by using easy techniques such as direct UV bleaching. The performance of phase modulators, Mach-Zehnder interferometers, and 2*2 space switches built with such polymers is already very promising. >

All-optical Gbit/s switching using nonlinear optical loop mirror

Abstract: The switching of a 20 Gbit/s pulse train at 2.5 Gbit/s in an all-fibre NOLM is demonstrated. An entirely semiconductor case powered configuration was used with a long loop (6.4 km) ensuring low power (10 mW) for the switching pulses.

All-optical polarisation switch with long low-birefringence fibre

Abstract: Nonlinear polarisation switching of picosecond pulses from the linear polarisation eigenstates of a 200 m-long low-birefringence spun fibre is reported. The relatively low switching peak power of 20 W is promising for applications to all-optical processing and intensity discrimination of ultra-short pulses.

Quadrature optical phase modulators for lightwave systems

Abstract: Optical communication methods and apparatus are disclosed for transmitting two or more optical signals with different optical carrier frequencies on a single optical fiber with high spectral efficiency. Each optical carrier is typically modulated with multiple modulated subcarriers. In one embodiment, an optical phase modulator provides cancellation of second order intermodulation products in each optical signal, thereby permitting the optical carrier frequencies to be spaced by 2f max , where f max is the maximum modulation frequency. In another embodiment, a single sideband optical phase modulator provides cancellation of second order intermodulation products and one signal sideband, thereby permitting the optical carrier frequencies to be spaced by f max . Quadrature optical phase modulators for simultaneous transmission of two independent baseband digital data signals or two independent subcarrier multiplexed signals are disclosed.

Semiconductor integrated circuit device with optical transmit-receive means

Abstract: A semiconductor integrated circuit device comprising a plurality of semiconductor packaging substrates arranged parallel to one another, a plurality of semiconductor integrated circuits mounted on each of the semiconductor packaging substrates, a circuit for electrically connecting the semiconductor integrated circuits, an optical signal transmitting circuit, electrically connected to the semiconductor integrated circuits, for converting an electric signal input by the semiconductor integrated circuits to an optical signal and outputting it to another semiconductor packaging substrate, and an optical signal receiving circuit, electrically connected to the semiconductor integrated circuits, for receiving the optical signal output from the semiconductor packaging substrate, converting the optical signal to an electric signal, and outputting the electric signal to the semiconductor integrated circuits.

Single sideband optical modulator for lightwave systems

Abstract: Optical communication methods and apparatus are disclosed for transmitting two or more optical signals with different optical carrier frequencies on a single optical fiber (52) with high spectral efficiency. Each optical carrier is typically modulated with multiple modulated subcarriers. In one embodiment, an optical phase modulator (42) provides cancellation of second order intermodulation products in each optical signal, thereby permitting the optical carrier frequencies to be spaced by 2fmax, where fmax is the maximum modulation frequency. In another embodiment, a single sideband optical phase modulator provides cancellation of second order intermodulation products and one signal sideband, thereby permitting the optical carrier frequencies to be spaced by fmax.

A recursive modular terabit/second ATM switch

Abstract: The author proposes a recursive modular architecture for a very large scale asynchronous transfer mode (ATM) switch. By extending the concept of the original knockout switch, the cell filtering and contention resolution functions are distributed over many small switch elements, which are arranged in a crossbar structure. The output ports of a switch fabric are partitioned into a number of groups by a novel grouping network to permit sharing of the routing paths in the same group. This partitioning and sharing concept is applied recursively to construct the entire switch elements. The technique of channel grouping for trunk circuits can be incorporated in the proposed ATM switch to improve the cell loss/delay performance while the cells' sequences are retained. A prototype circuit for the key switch element has been designed, and it has been shown that more than 4000 of the switch elements can be integrated into a VLSI chip with existing CMOS 1- mu m technology. >

Optical switching using fiber ring reflectors

Abstract: We present the results of studies of fiber ring reflectors that are pulse excited in the negative dispersion regime. An intensity-dependent fiber switch is proposed for improved thresholding and pulse output characteristics over those previously reported. Schemes for fiber switches relying on solitary-wave collision-induced phase shifts are also discussed. A pulse regenerator and logic gates are proposed, each capable of correcting timing drifts.

Optical switch using spatial light modulators

Abstract: A structure for optical interconnection is disclosed along with methods of manufacture and operation. In one embodiment, the structure consists of optical fibers connected to an array of microlenses, either through integrated waveguides or not, that direct light onto a mirror formed in a substrate, which reflects light to a spatial light modulator. The spatial light modulator in turn reflects the light back to another mirror, which reflects the light through another microlens array, through integrated waveguides or not, and out another optical fiber. The structure is manufactured by forming the mirrors out of the substrate, forming waveguides if desired, forming troughs for the fibers and the microlenses, attaching external pieces such as the fibers, the lenses, and the spatial light modulator package, and packaging the device to maintain alignment.

Ultrafast all-optical switching in Al/sub 0.18/Ga/sub 0.82/As directional coupler in 1.55 mu m spectral region

Abstract: The observation of all-optical switching in a nonlinear AlGaAs directional coupler using the nonresonant contribution to the intensity dependent refractive index, below half the bandgap, is reported. These results represent the first demonstration of an ultrafast device using semiconductor waveguides, where the throughput is not limited by absorption processes.

All-optical, all-fiber circulating shift register with an inverter.

Abstract: An all-optical fiber Sagnac interferometer switch and erbium amplifier have been combined to form an all-optical 254-bit circulating shift register with an inverter. This simple optical loop memory demonstrates the cascadability of Sagnac interferometer switches.

Wavelength-multiplexed optical communication system and optical amplifier used therefor

Abstract: An optical communication system comprises: a plurality of optical communication apparatus for communicating signals by using a plurality of communicating lights having different wavelengths; an optical transmitter for transmitting a controlling light having a different wavelength than any of the plurality of wavelengths; an optical transmission line for interconnecting the optical transmitter and the optical communication apparatus to transmit the communicating lights and the controlling light; an optical amplifier for amplifying the communicating lights and the controlling light transmitted over the optical transmission line; and control circuit for discriminating the controlling light amplified by the optical amplifier from the communicating lights and controlling a gain of the optical amplifier to keep a light intensity of the controlling light at a constant level.

Optical frequency division multiplexing network

Abstract: An optical frequency division multiplexing network includes first optical communication paths connected to terminals, respectively, a second optical communication path connected to the outside and a node composed of a selection unit for selecting signals having optical frequencies to be sent to the plurality of terminals, respectively, from signals transmitted through the second optical communication path in optical frequency division multiplexing, a conversion unit for converting the selected signals into signals having a single optical frequency and an output unit for producing the converted signals to the terminals through the first optical communication paths, respectively.

Integrated optical inverter using light amplifying optical switch (LAOS)

Abstract: An integrated optical inverter is demonstrated. Experimental results show good static input/output characteristics and an on/off ratio suitable for integrated optical logic. The simplicity of this circuit allows compact integration.

A rearrangeable multichannel free-space optical switch based on multistage network configuration

Abstract: A rearrangeable 128*128-channel optical switch based on a multistage network configuration is demonstrated. The properties of optical components required for achieving up to 1000*1000-channel switches are discussed, taking into account the diffraction limit and liquid crystal light modulator (LCLM) crosstalk. An examination of the insertion loss and crosstalk properties of the switch reveals an average loss and crosstalk of 7.9 and -21.2 dB, respectively, and worst-case loss and crosstalk of 11.0 and -12.8 dB, respectively. Such low-loss and low-crosstalk properties indicate that the proposed switch structure is suitable for a large-scale rearrangeable switch. >

1.4 ps rise‐time high‐voltage photoconductive switching

Abstract: We report on the generation of 825 V electrical pulses with 1.4 ps rise time and 4.0 ps duration using a pulse‐biased low‐temperature‐grown GaAs photoconductive switch triggered by an amplified femtosecond dye laser. Dependence of the pulse shape on both electric field and optical energy is observed and discussed.

Triggering technique for multi-electrode spark gap switch

Abstract: A spark gap switch having a mid-plane or triggering electrode is brought o a conductive state using a photoconductive switch or other suitable switch, closed by a laser pulse on other pulsed light source. The photoconductive switch is connected between one of the primary electrodes and the mid-plane electrode and brings the potential of the mid-plane electrode to the same potential as the primary electrode when the photoconductive switch is closed. The use of the photoconductive switch permits shorter closing times and eliminates the need for high voltage auxiliary triggering circuits. Plural photoconductive switches, which are triggered in a precise predetermined sequence, improve the operation of Marx generators and other multi-spark gap switch applications.

130 ps recovery of all‐optical switching in a GaAs multiquantum well directional coupler

Abstract: A significantly improved recovery time of 130 ps has been achieved in an all‐optical zero‐gap directional coupler containing multiple quantum wells. The mechanism for the all‐optical switching is due to free‐carrier induced refractive nonlinearities at near‐band‐gap resonant frequencies. The large reduction in the switch recovery time was obtained by the application of an external dc bias which sweeps out the carriers from the quantum wells. From our experimental results on the laser pulse width limited switch‐up time of 2 ps, we deduce that the contribution of self‐electro‐optic effect nonlinearity is negligible in this case.

Photonic cross-connect switch

Abstract: This invention relates to an optical cross-connect switch which is substantially loss-less and is transparent to signal bit rate, format and modulation scheme. The optical cross-connect switch can be comprised of at least two stages of chips coupled in tandem via optical fibers. Each chip can be of lithium niobate having a plurality of digital switch elements or directional couplers which, by means of an electric field, can selectively switch optical energy from one waveguide to another. The chips are coupled together via optical fiber amplifiers and the optical fiber amplifiers are pumped by optical pumps, e.g., 1.48 μm CW, laser pumps, coupled to appropriate nodes within either one or both of the chips. In operation, the pump energy is switched through the chips along with the optical data signals to pump only those optical fiber amplifiers which are in the optical data signal path.

High Gain Photoconductive Semiconductor Switching

Abstract: Switching properties are reported for high gain photoconductive semiconductor switches (PCSS). A 200 ps pulse width laser was used in tests to examine the relations between etectric field, rise time, delay, and minimum optical trigger energy for switches which reached 80 kV in a 50 /spl Omega/ transmission line with rise times as short as 600 ps. Infrared photoluminescence was imaged during high gain switching providing direct evidence for current filamentation. Implications of these measurements for the theoretical understanding and practical development of these switches are discussed.

First digital optical switch based on InP/GaInAsP double heterostructure waveguides

Abstract: A Y-junction digital optical switch based on InP/GaInAsP has been realised and operated using either carrier injection or carrier depletion. the switch functions with both TE and TM polarised light. In the case of current injection, 30 mA is enough to obtain a crosstalk up to 20 dB for TM polarisation and 10 dB for TE polarisation. >

16*16 single chip optical switch array in lithium niobate

Abstract: The design and construction of a lithium niobate 16×16 guided wave switch with a Benes architecture is described. The switch is interfaced to polarisation maintaining optical fibre, has 56 elements, switching voltages ranging between 35 and 60 V and crosstalk suppression of 20 dB at 1.3 μm wavelength.

All-optical switching in a 200-m twin-core fiber nonlinear Mach–Zehnder interferometer

Abstract: All-optical switching is demonstrated in a 200-m-long fiber nonlinear Mach–Zehnder interferometer. The only stabilization mechanism used is passive enclosure of the interferometer. Stable operation is obtained by using a twin-core fiber. The experiment demonstrates the feasibility of use of fiber nonlinear Mach–Zehnder interferometers for ultrafast switching and pipeline logic.

Sagnac optical logic gate

Abstract: An optical switch employs a modified sagnac arrangement that includes a sagnac loop (10,11) and a coupler (20) for injecting a signal into the loop and developing thereby two signals (MARK,REF) that travel along the loop in opposite directions. The coupler has at least one signal port that is accessible from outside the switch. In addition, a coupler (30) is included to inject a pump signal into the loop to travel through the loop only in one direction. The loop is made of, or comprises, a material (11) that has a controllable propagation speed. More particularly, the propagation speed in the material is a function of, for example, the intensity of the pump signal. The switch action is attained when the applied signals are in the form of pulses with pulse widths and relative positions controlled to achieve a particular interaction. The switch action is observed by sending a pulse down a sagnac loop and observing its return. Switching is activated by either sending or not sending a pump pulse concurrently with the signal pulse that is sent down the sagnac loop. When a pump pulse is sent, it is timed to orient itself so that the pulse that propagates faster through the loop precedes the pulse that propagates slower. While propagating through the loop, the faster pulse overtakes and surpasses the slower pulse, causing the two pulses to traverse each other. In this manner the pump pulse affects the propagation speed of the pulse sent through the sagnac loop and modifies the phase of the affected pulse as it re-enters the sagnac coupler. When the intensity of the pump pulse is properly controlled, the phase shift caused by the pump pulse is such that no output appears at the port of the sagnac arrangement.

Demonstration of optical switching by means of solitary wave collisions in a fiber ring reflector.

Abstract: We have demonstrated the use of solitary wave collisions in optical pulse switching. Our apparatus consisted of a fiber ring with 11 sections of polarization-maintaining fiber, with successive sections fusion spliced with the axes rotated 90 deg. The configuration yielded enhanced transmission (autocorrelation contrast ratio 2.82:1), in agreement with expectation for this number of sections and the unoptimized fiber coupler that was used. Design criteria for complete switching are presented.

Optical switching in a resonant tunneling structure

Abstract: We describe the interaction of light pulses with a GaAs/AlAs resonant tunneling structure. We demonstrate that light with an average power of less than 10 μW can induce switching, and show that switching is accompanied by a change in the optical absorption. These results suggest a number of new applications for the resonant tunneling structure, including light‐by‐light switching.