Abstract: A multiplexer for a wavelength division multiplexed optical communication system includes an optical circulator with at least first, second, third and fourth circulator ports. An optical fiber with a first optical transmission path is coupled to the first circulator port and carries a wavelength division multiplexed optical signal that includes signals 1−n. A second optical transmission path is in optical communication with the second circulator port. A first laser is coupled to the second optical transmission path. The first laser reflects the 1−n signals and adds a signal n+1. A control loop is coupled to the first laser. In response to a detected change in temperature the control loop sends a signal to adjust a voltage or current supplied to the first laser and provide a controlled frequency and power of an output beam.

Abstract: A tunable semiconductor laser system includes a laser with a semiconductor active region positioned between upper and lower confining regions of opposite type semiconductor material. First and second reflective members are positioned at opposing edges of the active and confining regions. A wavelength tuning member and a temperature sensor are coupled to the laser. A control loop is coupled to the temperature sensor and the tuning member. In response to a detected change in temperature the control loop sends an adjustment signal to the tuning member and the tuning member adjusts a voltage or current supplied to the laser to provide a controlled output beam of selected wavelength.

Abstract: A monolithic vertical optical cavity device built up along a vertical direction. The device has a bottom Distributed Bragg Reflector (DBR), a Quantum Well (QW) region consisting of least one active layer grown on top of the bottom DBR by using a Selective Area Epitaxy (SAE) mask such that the active layer or layers exhibit a variation in at least one physical parameter in a horizontal plane perpendicular to the vertical direction and a top DBR deposited on top of the QW region. A spacer is deposited with or without SAE adjacent the QW region. The device has a variable Fabry-Perot distance defined along the vertical direction between the bottom DBR and the top DBR and a variable physical parameter of the active layer. The varying physical parameter of the active layers is either their surface curvature and/or the band gap and both of these parameters are regulated by SAE. The monolithic vertical cavity device can be used as a Vertical Cavity Surface Emitting Laser (VCSEL) or a Vertical Cavity Detector (VCDET).

Abstract: A tunable semiconductor laser system includes a laser with a semiconductor active region positioned between upper and lower confining regions of opposite type semiconductor material. First and second reflective members are positioned at opposing edges of the active and confining regions. A wavelength tuning member and a temperature sensor are coupled to the laser. A control loop is coupled to the temperature sensor and the tuning member. In response to a detected change in temperature the control loop sends an adjustment signal to the tuning member and the tuning member adjusts a voltage or current supplied to the laser to provide a controlled output beam of selected wavelength.

Abstract: A method and circuitry are provided for generating a phase shift in the recovered clock in a high speed, digital data recovery phase locked loop. Since phase step injection can be done in a closed loop environment, the dynamic of the real time phase step response of the PLL can be analyzed using a phase meter. In an open-loop environment, the output of the phase meter with a step response of 60 degree phase shift tracks closely with the internal RC response at the multi-phase outputs of the PLL's phase-to-frequency converter. Since the register and capacitor values vary with process, the scheme for verifying the relative accuracy of the PLL's internal filters can be verified without actually probing the device.

Abstract: An electronic circuit suitable for sampling an incoming data bit stream in order to recover the information contained in the data stream contains an input section, a reference section, and a comparing section. The input section produces a ramp signal that switches between a first endpoint voltage and a second endpoint voltage in a periodic manner. The reference section furnishes a plurality of reference voltages between the two endpoint voltages. The comparing section compares the ramp signal to the reference voltages to produce corresponding sampling signals. Each sampling signal makes a first voltage transition as the ramp signal passes a corresponding reference voltage in going from the second endpoint voltage to the first endpoint voltage. Accordingly, the first transitions of the sampling signals occur in groups, each group being spread out in time during part of a period of the ramp signal. A data sampling portion of the circuit utilizes the sampling signals to sample the input data bit stream.

Abstract: A phase-to-frequency converter uses a triangular waveform synthesizer to generate a triangular wave using both PDM and a DC modulation scheme. A 4-bit PDM and associated logic generates the PDM output waveform with polarity information and two switching waveforms that encode the DC level information to provide a resultant sum. The resulting waveform, after filtering, is the multiple phases of the triangular waveform. The generated multiple phases of the triangular wave are then modified by reducing the ramp rate at appropriate points to suppress the third harmonic and its multiples. The ramp rate is proportional to the pulse density output of the Pulse Density Modulator. In one embodiment, the rate of the PDM output is reduced by one half during appropriate periods by gating the output by its clock, thereby reducing its density by one half during those periods.

Abstract: A triangular waveform synthesizer for a phase-to-frequency converter generates a saw tooth and triangular wave using both PDM and a DC modulation scheme. To minimize both delay and logic, while continuing to provide reasonable resolution, a 4-bit PDM and associated logic generates the PDM output waveform with polarity information and two switching waveforms that encode the DC level information to provide a resultant sum. The resulting waveform, after filtering, is the triangular waveform. Since the switching and adding of the DC levels occurs in real time, the actual delay for the resultant triangular wave is only that of the 4-bit PDM.

Abstract: A programmable multiphase clock divider for selectively frequency dividing a multiphase input clock to provide a lower-frequency, self-aligned, multiphase output clock includes a counter, combinational logic circuitry, a multiphase signal generator and a multiplexor. With the counter serving as the sole frequency divider element, multiple phase-aligned clock phases are generated which are then programmably multiplexed to provide the desired frequency-divided, self-aligned clock phases. The counter, in response to a preset signal and an input clock phase, generates a multibit count signal, one bit of which forms the first output clock phase. The combinational logic circuitry receives a programming signal for decoding the multibit count signal to generate the counter preset signal and an output control signal.