Abstract: An RF-lightwave transmitter performs successive conversions of an information-bearing input signal in order to generate an output signal suitable for transmission in a wireless communications system. The transmitter includes a high-efficiency FM laser connected to a FM discriminator. In operation, the laser converts an RF signal into a frequency-modulated optical signal, and the discriminator converts this signal into an amplitude-modulated optical signal. The discriminator performs its conversion using a high slope-efficiency linear transfer function which ensures that the AM optical signal varies in accordance with a desired operational performance. The transmitter also includes a photodiode which converts the AM signal output from the optical discriminator back into an RF signal for transmission. Experimental results demonstrated that a transmitter of this type is able to realize greater than 10 dB RF insertion gain at less than 0 dBm optical power, with a high spurious-free dynamic range and low noise.

Abstract: An optical gain medium, and a method for forming the same, is provided that exhibits lower wavelength crosstalk when configured as an optical amplifier than prior art optical gain media. The optical gain medium of the present invention includes a buried heterostructure waveguide fabricated in a multiple quantum well (MQW) region. The MQW region in which the buried heterostructure waveguide is located exhibits a continuously changing bandgap as a function of position along the waveguide direction, preferably such that the gain provided by the optical gain medium changes exponentially as a function of position along the waveguide direction. In a preferred embodiment, the MQW region in which the buried heterostructure waveguide is buried is grown using a selective-area-growth (SAG) technique, and is made up of at least two quantum wells, with at least one of the quantum wells having a size and composition that vary as a function of position along the waveguide direction.

Abstract: The present invention provides tunable optical system, and a method for forming the same, that exhibits a broader tuning range with fewer components than prior art tunable optical systems. The tunable optical system of the present invention includes a plurality of wavelength routers, each having a different optical channel resolution, optically coupled to a plurality of optical amplifier arrays. The free spectral range of each of the second and subsequent wavelength routers is equal to a total bandwidth of one of its respective grating orders. The system is tuned by selectively activating optical amplifiers in each of the optical amplifier arrays. The tunable optical system of the present invention can be used to make tunable semiconductor emitters, receivers and filters.

Abstract: A system and method of testing multiple edge-emitting lasers on a common wafer is provided. This is accomplished by providing, for each edge-emitting laser on a common fabrication wafer, a structure that re-directs a portion of the edge-emitted light from each edge-emitting laser in a direction such that the re-directed portion from each edge-emitting laser can be measured while the edge-emitting lasers are still on the fabrication wafer. Each edge-emitting laser on the fabrication wafer can therefore be easily tested before cleaving or breaking the wafer into multiple pieces.

Abstract: An edge-emitting laser having an edge-emitting output and a surface-emitting output. The edge-emitting laser has a resonator having a high order grating, preferably a second order grating capable of producing an edge-emitting component and a surface-emitting component. A waveguide is also located in the resonator and a cap layer is located above the waveguide and grating. The cavity is tested by taking measurements from the surface-emitting component eliminating the need for taking measurements from the edge-emitting component which is time consuming and expensive.

Abstract: A system and method for compensating for unwanted modes in multimode fiber transmissions includes a detector that receives an optical signal transmitted through a multimode optical fiber and converts the transmitted optical signal to a detector signal, an adaptive equalizer that generates an adaptive equalizer signal that, when combined with the detector signal, compensates for unwanted modes in the detector signal, and an adder that combines the adaptive equalizer signal with the detector signal.

Abstract: An integrated coherent transceiver capable of being operated with only one below threshold FP mode is described which can be used for both receiving downstream signals and transmitting upstream signals with either FSK or ASK format. The device allows the full tuning range of distributed-Bragg-reflector ("DBR") lasers to be utilized to achieve approximately one thousand channels in a local access system with 1 GHz channel spacing. The sensitivity can be further enhanced by obtaining balanced operation (without changing the simple device structure) to cancel the laser intensity noise.

Abstract: A lightwave communication system is disclosed in which an integrated receiver is realized as a distributed Bragg reflector (MQW-DBR) laser structure biased at or below threshold. The receiver functions simultaneously as a tunable filter, optical amplifier, photodetector, and, if desired, as an FSK discriminator. It is also disclosed that the lightwave receiver also is capable of half duplex operation as a lightwave transmitter using the same DBR laser structure. The disclosed receiver eliminates complex coupling of the many different element realized by the integrated, multifunction structure.