Abstract: An integrated, single output port, tunable multiple wavelength laser apparatus produces one of Na Nb wavelengths using only Na plus Nb selection signals. Each of Nb ports can output Na of the laser wavelengths, the port being selected by the Nb control signals and the particular one of the Na wavelengths being selected by the Na control signal. An Nb×1 router combines the signals from the Nb output ports into a single output.

Abstract: A wavelength conversion apparatus and method uses four wave mixing of a first wavelength and a control wavelength in an optical fiber to convert the first wavelength to a desired wavelength. Four wave mixing is produced by operating the optical fiber at a predetermined input power density and by using a fiber length which provides substantial Raman gain. The first wavelength is converted to a higher wavelength by using the higher wavelength four wave mixing signal and converted to a lower wavelength by using the lower wavelength four wave mixing signal.

Abstract: Temperature compensation of a wavelength-division-multiplexed (WDM) passive optical network (PON) communication system uses power measurements from each of it remote nodes (RNs) to adjust the frequency of an associated multifrequency laser (MFL). Changes in the power level at each RN caused by frequency drift of its waveguide grating router (WGR), due to changes in the WGR temperature, is determined by monitoring the power level received at each RN and corrected by appropriate changes in the temperature of the associated MFL. The WGR uses one output port (e.g., channel 1) which is looped-back through the WGR a second time to increase the temperature sensitivity of the power measurements. A temperature-control algorithm controls the temperature of the MFL as a function of changes in the received power at the WGR.

Abstract: An optical beam switch is designed for improved serviceability by mounting two fiber optic beam deflection arrays to face the front of a rack assembly. Inside the optical beam switch, a reflecting device is located behind each of the two fiber optic beam deflection arrays and used to reflect the light beams between the two fiber optic beam deflection arrays. Front access to the two fiber optic beam deflection arrays is then readily available whether the optical beam switch is mounted horizontally or vertically in the rack assembly.

Abstract: The spectral distortion introduced by stimulated Raman scattering (SRS) in an optical fiber transmission system has been determined to always be linear on a dB/nm scale and depend solely on the total input power and not on the input power distribution. By maintaining the total input power to the fiber constant, the resulting Raman gain tilt may be compensated for or canceled by using an optical filter.

Abstract: A Differential Phase Shift Keying (DPSK) optical transmission system provides time division multiplexing, channel routing and channel add/replace functions. The DPSK transmitter comprises a laser to generate an optical carrier signal; a delay encoder to provide a different delay for each of a plurality, M, of input signal channels; and a M channel phase modulator which phase modulates the optical carrier signal with each of the differently delayed M input signal channels to form a Time Division Multiplexed (TDM) phase modulated optical signal. A DPSK receiver demodulates a received TDM phase modulated optical signal. The system may also include apparatus to route, add, and replace TDM channels.

Abstract: A router combines free-space and guided wave optics to drastically increase the number of channels used in WDM transmission systems. The two-stage router uses the partial demultiplexing characteristic of an arrayed waveguide router (AWR) combined with a free-space optical router to fully demultiplex an input WDM signal. The two-stage router can be used to obtain output wavelength signals in either one- or two-dimensional arrays.

Abstract: A birefringent filter includes an input optical apparatus for receiving an input optical beam and producing therefrom parallel first and second optical beams offset in a first direction and having the same polarization. A birefringent filter unit receives the first and second polarized optical beams and produces a first and second elliptically polarized optical beams. An output optical apparatus combines predetermined components of the first and second elliptically polarized optical beams to form a first and second elliptical polarized output beams. The two output beams have intensities that vary inversely, in a periodic manner, as a function of frequency of the input optical beam.

Abstract: A restoration procedure for use in bidirectional multiplex section-switched ring transmission systems re-establishes a connection path by using a loopback connection at nodes bordering the failure and by then establishing a jumpered connection path, for each active tributary affected by the failure. The jumpered connection path at affected node eliminates any unnecessary loop formed in the re-established connection path caused by the loopback connection at the border nodes. There is stored in memory at each node (1) the provisioned connection path, (2) the jumpered path, and (3) a jumper flag is set indicating that a jumper connection exists. When the failure is cleared the (1) jumpered path is removed and its record erase from memory, (2) the provisioned connection path is restored, and (3) the jumper flag is reset. Advantageously, the this operation can be programmed into existing node controllers and is compatible with existing restoration procedures.

Abstract: A multichannel laser is based on an interleaved chirped waveguide grating router. An interferometric modulator is incorporated inside a laser cavity by means of a waveguide grating router and enables independent modulation of any of the wavelengths of the multichannel laser. The interferometric modulator operates independently of the wavelength selection elements of the waveguide grating router used to select the wavelengths of the multichannel laser.

Abstract: Laser wavelengths used in a WDM system are stabilized using a known accurate electrical frequency standard. The laser wavelengths are stabilized using a first frequency locking circuit which individually locks each laser wavelength to a different resonant frequency of an optical interferometer and a second frequency locking circuit which locks a different resonant frequency of the optical interferometer to an accurate electrical frequency standard signal. The known accurate electrical frequency standard prevents the resonator from drifting and the resonator prevents the WDM system lasers from drifting.

Abstract: A technique is described for determining the performance of substrate-side emitting VCSELs formed on a wafer. The technique involves forming top-emitting VCSELs on the same wafer as bottom-emitting VCSELs and then testing the top-emitting VCSELs and using the results to determine the performance of the bottom-emitting VCSELs of the wafer.

Abstract: Changing the index in the two output branches of a Y-branch optical waveguide in opposite directions, in amounts which are controlled by electrical signals applied to the branches, is used to control the chirp of the signal outputted from the Y-branch optical waveguide. In this manner, predetermined amount of chirp can be add to or subtract from an input signal to the Y-branch optical waveguide. The Y-branch optical waveguide can be fabricated using Group II-VI, Group III-V or Group IV material systems or using an insulating material, such as lithium niobate. The output branches of a semiconductor implemented Y-branch optical waveguide can be fabricated to each include a multiple quantum well for controlling the refractive index of that branch in response to an electrical signal.

Abstract: A dynamically and chromatically variable transmissivity apparatus (e.g., a channel equalizer or an add-drop circuit) controls channel powers in wavelength-division multiplexed systems. The input WDM signal is split into two components, in one component a phase shift is added to the wavelengths needing equalizing, the two signal components are then recombined. The phase shift added at each wavelength determines the amount of equalization obtained for that wavelength. For a decrease in equalization (i.e., attenuation) range the apparatus exhibits a decrease in insertion loss.

Abstract: An optical demultiplexer demultiplexes an N channel multiplexed optical data signal, at a first data rate, into N signal data channels. The demultiplexing is provided by N optical receivers, each receiver receiving a clock signal and the multiplexed optical data signal which is demultiplexed into a different one of the N signal data channels. In another embodiment, a shared photodetector converts the received multiplexed optical data signal into a multiplexed data signal which is then used by all of the N receivers.

Abstract: A system provides short range wireless data communication from a central control point (e.g., interrogator) to inexpensive endpoints (e.g., tags). The endpoints utilize the technology of modulated backscatter for transmission from the tags to the interrogator. The system uses a new downlink protocol for data transmission from the interrogator to the tags and a new uplink protocol for data transmission from the tags to the interrogator. Both protocols use a backoff/retry algorithm to randomly retransmit any non-acknowledged messages. System capacity from the tags to the interrogator is further enhanced by the use of uplink subcarrier frequency division multiplexing.

Abstract: A differential optical signal receiver includes an interference-rejecting circuit to provide enhanced interference signal rejection. The differential optical signal receiver includes a differential optical signal detector for detecting a received differential optical signal and converting it to a differential electrical signal. An interference-rejecting differential electrical circuit, including a common source load, processes the differential electrical signal so as to reject any electrical interference signal other than said differential electrical signal.

Abstract: A split-architecture modem splits the physical layer protocol into a logical operations portion and a signal processing portion. A first processor (e.g., a general purpose processor (GPP)) of the modem performs the logical operations of the physical layer protocol along with the data link layer protocol. A second processor (e.g., a digital signal processor (DSP)) of the modem performs the signal processing portion of the physical layer protocol.

Abstract: We have determined that unlike the most multimode silica fiber, multimode polymer fiber often exhibits a delay characteristic that has a broad low dispersion region where propagation delay of spatially restricted optical pulses remains relatively constant. This low dispersion region is centered around the center axis of the fiber core as a function of launch position. By directing a transmitted optical pulse to this region, we have determined that optical pulse dispersion can be significantly reduced without the need for using the prior art technique of using a single mode fiber spliced in series with the multimode fiber to reduce dispersion. A polymer fiber based optical transmission system using this arrangement exhibits relaxed alignment tolerances between the optical source and polymer fiber, while reducing dispersion and increasing bandwidth-length product.

Abstract: In soliton transmission, third order dispersion of the transmission fibers tends to cause unacceptable variation in the filter strength parameter, .eta. over the wide wavelength bands required for massive wavelength division multiplexing (WDM). The effect of dispersion is substantially eliminated by varying the mirror reflectivities R(.lambda.) of etalon filters with wavelength, such that the strength (.eta.) parameter, in soliton units, essentially remains at the optimal value across the entire WDM transmission band.