Abstract: An optical pumping apparatus provides pumping for a Raman amplifier across either the C-band alone, or across both the C-band and the L-band. A first pump unit provides the optical pump energy necessary for a flat gain response in the C-band. A second pump unit, operating as an upgrade module, can be activated to expand the pumping range into the L-band. The second unit provides both the pump energy for the expanded portion of the gain spectrum, as well as pump energy for the C-band that compensates for any disruption of the gain profile, so that a flat gain response is maintained across both the C-band and the L-band.

Abstract: Conventional retroreflection mirrors in the form of right angle prisms are quite sensitive to beam position and beam angle errors. Manufacturing and assembly tolerances are also a cause of concern in conventional devices. Accordingly, the present invention solves these aforementioned problems by providing a retroreflection device comprising: a beam director, preferably in the form of a Wollaston prism; a polarization rotator, preferably in the form of a quarter wave plate; and a flat reflective surface, such as a plane mirror. The device of the present invention is far less sensitive to beam angle alignment and is completely independent of the beam position. The present invention is particularly useful as a beam splitter for directing orthogonally polarized beams of light back along parallel paths in an interleaver apparatus.

Abstract: A method for designing an avalanche photodiode for high bit rate or high speed applications is disclosed. The photodiode is made up of a multiplication layer of a first semiconductor material, an absorption layer of a second semiconductor material and a field control layer of a third semiconductor material having. The field control layer has a moderate doping of a first type dopant and is intermediate between the multiplication and absorption layers. A central region of the multiplication layer is diffused with a second type dopant which results in a diffused region having a greater thickness in the center than in the periphery of the diffused region.

Abstract: An optical filter assembly is provided which includes a first optical filter and a first counteracting ring. The first optical filter is of a filter material that transmits a selected transmission range within a wider range of wavelength of light, and reflects another selected reflection range of the wavelengths. The filter material has a refractory index, whereby heating of the first optical filter tends to cause an increase in refractory index with a corresponding increase in the transmission range in a first direction. The counteracting ring is attached to the first optical filter so that at least some of the light transmits through an aperture in the counteracting ring. Heating of the first counteracting ring causes enlargement of the first counteracting ring, which stretches the first optical filter. The selected transmission range is thereby at least partially stabilized.

Abstract: The most common method of testing the various aspects of light traveling in a waveguide includes tapping a portion of the light and directing the tapped portion at an appropriate sensor. Conventionally, the simplest method for tapping light utilized a fused fiber coupler; however, even this method requires additional fiber splicing and management steps that increase manufacturing costs. The present invention uses a beam splitter, positioned inside a centerpiece sleeve in the path of the light, to direct a portion of the beam through the wall of the centerpiece sleeve to a monitoring sensor, preferably a photodiode. The centerpiece sleeve includes a window, which is at least partially transparent to the light, enabling the tapped portion of the light to reach the monitoring sensor. Preferably, the centerpiece sleeve is manufactured entirely out of glass.

Abstract: A high power laser optical amplifier system for material processing comprises multiple stage fiber amplifiers with rejection of propagating ASE buildup in and between the amplifier stages as well as elimination of SBS noise providing output powers in the range of about 10 &mgr;J to about 100 &mgr;J or more. The system is driven with a time varying drive signal from a modulated semiconductor laser signal source to produce an optical output allowing modification of the material while controlling its thermal sensitivity by varying pulse shapes or pulse widths supplied at a desire repetition rate via modulation of a semiconductor laser signal source to the system to precisely control the applied power application of the beam relative to the thermal sensitivity of the material to be processed. The high power fiber amplifier system has particular utility in high power applications requiring process treatment of surfaces, such as polymeric, organic, ceramic and metal surfaces, e.g.