Abstract: A system and method for output power controlled stabilizing system comprises a wavelength limiter which minimizes the wavelength variation of a laser signal light. The wavelength limiter comprises a first and second clamping circuit. The first clamping circuit receives an offset voltage, compares the offset voltage to a first predetermined reference voltage, and outputs the voltage difference between the offset voltage and the first predetermined reference voltage. If the offset voltage rises higher than the first predetermined reference voltage, the first clamping circuit then clamps and keeps the power of the output power controlled wavelength stabilizing system from increasing. The second clamping circuit receives the offset voltage, compares the offset voltage to a second predetermined reference voltage, and outputs the voltage difference between the offset voltage and the second predetermined reference voltage.

Abstract: Optical transmit amplifier (24) fault indicator system (46), (78), and (80) indicates the failure of optical transmit amplifier (24) and includes an input loss circuit (46), an output failure circuit (80), and a modulation detector circuit (78). The modulation detector circuit (78) receives a portion (76) of the optical output signal (74) for determining therefrom that a failure in modulation exists in optical output signal (74) of optical transmit amplifier (24). The modulation detector (78) includes a modulation conversion circuit (82) and (84) for converting modulation in the optical output signal (76) into a measurable signal having a level within a first predetermined range in the presence of modulation and a second predetermined range in the absence of modulation. The modulation detector circuit (78) converts the measurable signal to a DC signal and produces a loss of modulation alarm signal (114) in response to a loss of modulation.

Abstract: Various optical amplifier configurations are disclosed. In one configuration, an optical amplifier provides an amplified output signal through use of a pumping device. The output signal is split to an output and a feedback input. The feedback signal is converted to a current which is sensed by a controller. The controller adjusts the amount of current to the pumping device in various instances. In one instance, the current is controlled to prevent overdriving the pumping device. In another instance, the current is controlled to maintain the output signal at a substantially constant level. In another configuration, the optical amplifier is coupled to a ratio computation block which measures the operating efficiency of the pumping device. Additional components detect an undesirable efficiency and provide a warning of the same.

Abstract: A method and system for multiple WDM signal compensation compensates optical chromatic dispersion for a plurality of optical signals having predetermined frequencies and each traveling in an optical path associated with the wavelength division multiplexer that forms a multiplex optical signal from the plurality of optical signals. The invention first undercompensates the multiplex optical signal by a predetermined amount so that each of the optical signals has an associated residual optical chromatic dispersion. Then, either before or after undercompensating of the multiplexed optical signal each of the optical signals is individually compensated to remove therefrom the residual chromatic dispersion. The system and method permit simultaneous and independent control of optical dispersion at any desired wavelength, as well as selection of matching compensation for optical transmitters prior to installation. The result is an increase in the usable wavelength range of optical signals for WDM networks.

Abstract: The present invention provides a method and system that compensate end-to-end optical dispersion for a fiber-optic cable having a plurality of predetermined compensations sites to within a predetermined dispersion limit using a predetermined dispersion compensation increment. With the method and system, the predetermined dispersion compensation increment may exceed both the predetermined compensation limit as well as the compensation limit divided by the number of sites. The method includes the steps of compensating optical dispersion using the compensation increment for each of the plurality of predetermined compensation sites to yield an end-to-end optical dispersion compensation within the predetermined optical dispersion limit. This may include optical dispersion over-compensation at some sites and optical dispersion under-compensation at other sites.

Abstract: Many prior control circuits inject a small amplitude control tone into the prime signal path where the distortion added to the prime or main signal by the control tone does not present a significant corruption of the prime signal. This control tone is detected and, based on the detected parameters, the prime signal is adjusted as to one of its parameters such as amplitude. If there are variable frequency spurious signals that may produce products within the bandwidth of the control system, the operation of the control circuit can be completely disrupted. The present invention overcomes the prior art problem by continuously sweeping the frequency of the control tone whereby the detection of the spurious signals in the operation of the control circuit occurs such a small percentage of the time that the control circuit can maintain reliable control operation.

Abstract: A service tool is provided for a fiber optic connection system in which a pair of facing fiber optic connector ends are collinearly aligned by a tubular alignment insert therearound, all within an outer concentric tubular connection sleeve. After withdrawal of one of the connectors, the tool serves as an extraction tool for removing the alignment insert around the connector end within the outer concentric sleeve. The tool has another side serving as a test gauge for determining the presence or absence of the alignment insert around the end of the fiber optic connector within the outer concentric connection sleeve without looking into the sleeve.

Abstract: A digital phase detector is provided for NRZ data phase detection. In a phase locked loop application, the detector generates a variable duration pulse between a data transition and a positive transition of the recovered clock, and generates a fixed duration pulse between the positive clock transition and the next negative clock transition. The difference in duration between the variable and fixed pulses provides phase indication.

Abstract: A digital sampling phase detector is provided for NRZ data phase detection and is particularly suited for applications with long sequences of no data activity. In a phase locked loop application, phase error circuitry detects the phase difference between data transitions and clock transitions of the recovered clock, and outputs phase error signals corresponding to various durations between designated transitions. Sampling switching circuitry responds to a data transition to initiate a measuring interval by forcing the output of the phase error circuitry to a low impedance follower mode to permit sampling, and responds to a designated clock transition to terminate the measuring interval by forcing the output to a high impedance state. The sampling switching circuitry prevents the sampled signal level from drifting during a non-measuring interval, and the reduction of drift significantly reduces jitter in the recovered clock. The sampling function is provided in combination in a high speed ECL phase detector.

Abstract: A phase-locked loop apparatus for deriving clock pulses from return-to-zero data pulses is disclosed. It includes a phase detector for computing the difference, in time, between that portion of a detected data pulse which occurs before a clock pulse edge and the portion after the clock pulse edge. The difference, once computed, is held for a long period thereafter and is used to drive a voltage controlled oscillator. The voltage controlled oscillator generates the clock pulses which are applied to the phase detector and which comprise the output of the apparatus.

Abstract: A method of making a compound roll of the type having a shell portion of a material that has a high hardness and wear resistance and a core portion forming the center core and neck sections of a material that has a low alloy content and a relatively low hardness so as to be highly resistant to breakage, which method comprises the steps of precasting the shell portion in the form of a hollow cylinder having the desired external and thickness dimensions, setting the shell portion on top of a neck forming mold section with the longitudinal axes of the shell portion and the mold section extending vertically, positioning an electrode of an electro-slag melting unit within the interior of the shell portion and the neck mold section, the electrode being made of material which in the remelted and subsequent resolidified condition will have the desired properties for the center core and neck sections, and passing electric current through the electrode to cause melting thereof to progressively fill the mold section and