Abstract: A multiple port reflection based circulator using a thermally expanded multiple core fiber. The circulator includes optical components to separate, rotate, and combine orthogonally polarized components of light in order to propagate light in one direction among consecutive cores of the fiber. The first and last cores of the fiber also being consecutive cores. The thermally expanded multiple core fiber enabling coupling to the circulator without the use of lenses.

Abstract: An optical fiber having a thermally expanded multiple core section. One such multiple core section may be fabricated by fusing together non-etched multiple fiber claddings resulting in the multiple cores having expanded mode fields that are positioned in close proximity to each other in a common cladding, without signal coupling between the cores. The close proximity of the cores having expanded mode fields may allow for tighter alignment of light waves propagated from one core to other cores.

Abstract: Improved optical devices, systems, and methods for selectively directing optical signals generally based on a Mach-Zehnder interferometer. Through accurate control of the phase relationship, the Mach-Zehnder interferometer allows optical signals to either be cumulatively combined so as to enhance the transmitted signal strength, or destructively combined so as to effectively prevent transmission from an optical signal port. This phase relationship can be controlled using a nonreciprocal device having a pair of retarder plates disposed along one of the two legs of the Mach-Zehnder interferometer so as to provide an optical isolator or circulator.

Abstract: A laser source with an extremely stable output is provided. A laser diode has an output intensity centered at a peak wavelength which is responsive to a control signal. First and second fiber Bragg gratings are coupled to the laser diode. The first fiber Bragg grating having a reflectivity centered about a first wavelength and the second fiber Bragg grating having a reflectivity centered about a second wavelength different from the first wavelength. Each of the first and second fiber Bragg gratings generates a feedback signal responsive to the reflectivity of the fiber Bragg grating and the output intensity of the laser diode. A controller connected to the laser diode generates the control signal responsive to the feedback signals from the first and second fiber Bragg gratings so that the peak wavelength of the laser diode is maintained at a fixed wavelength between the first and second wavelengths.

Abstract: The present invention provides fiber optic couplers for use with at least three optic fibers. The optic fibers arranged in a linear array, that is, the optic fibers are coupled side by side. The fibers along either end of the linear-array are coupled only to a single fiber, while the remaining fibers are generally coupled between only two adjacent fibers. Generally, at least one of the fibers has a propagation constant different that the other fibers. Such variations in the propagation constant are used to vary the coupling coefficients among the fibers of the linear-array, thereby providing a repeatable mechanism, to vary coupled power ratios among the fibers of the coupler. Theoretical calculations and empirical experience have shown that varying the propagation constant of fibers among a linear-array, generally by pre-pulling the fibers by varying amounts, allows repeatable manufacturing of 1.times.3, 1.times.4, 4.thrfore.3, 1.times.N and even N.times.N fiber couplers having even coupled power ratios.

Abstract: The present invention provides for a system for the precision optical coating of substrates and a method of operating the system. The system has a vacuum chamber, a plasma source in the vacuum chamber, a plurality of e-beam evaporation units which generate a vapor of optical coating material in the vacuum chamber, and a plurality of stations, each station holding one substrate and rotating the substrate during deposition of the optical coating material upon the substrate. Each of the stations has an optical monitoring unit which monitors in situ the deposition of the optical coating material upon the corresponding substrate. With the described system, high production rates of precision optical elements, such as narrow bandpass optical filters, can be achieved.

Abstract: Tuned optical filters, filter systems, and methods for tuning filters make use of a tilted filter rotated about an oblique axis of a collimating lens or other structure. This rotation varies an angle of incidence of an optical signal directed at the filter at an oblique angle to the axis of rotation. Very fine adjustments of optical filters such as for tuning a first narrow band pass filter to match a center wavelength of another narrow band pass filter, can be provided with small angles between the axis of rotation and a normal to the filter surface, and also between the axis of rotation and the optical path for the incident light. Mechanical adjustment to the filtering frequency is facilitated by making use of a rotational motion about the axis of a GRIN collimating lens.

Abstract: Polarization combiners and dividers are used in combination with WDM multiplexers and demultiplexers to create fiberoptic network systems with increased bandwidth and number of network users. Besides wavelength, the state of polarization of the optical signals creates different communication channels for the network system. The present invention is adaptable to many different fiberoptic network arrangements.

Abstract: A fiberoptic coupler capable of many functions is presented. The basic fiberoptic coupler has a first sleeve, a second sleeve, a first collimating GRIN or conventional lens, and a second collimating GRIN or conventional lens. The first sleeve holds end sections of two or more input optical fibers along the longitudinal axis of the sleeve. The second sleeve holds an end section of at least one output optical fiber. The end face of the second sleeve faces the first sleeve end face. The first collimating GRIN or conventional lens in front of the first sleeve end face collimates light signals from the input optical fibers and the second collimating GRIN or conventional lens in front of the second sleeve end face focusses light signals from at least one of the input optical fibers into the single output fiber, or at least one of the output optical fibers. With only one output fiber the coupler operates as a combiner.

Abstract: A fiber Bragg grating DFB-DBR interactive laser is provided by an optical fiber section which is doped with at least one gain-inducing material. At each end of the section there is a fiber Bragg grating which operates as part of a fiber DBR laser. Between these two gratings there is a third fiber Bragg grating which has a 90.degree. phase shift region. The third fiber Bragg grating effectively operates as part of a fiber DFB laser. Each of the fiber Bragg gratings has a narrow reflective linewidth centered about the same wavelength so that the optical fiber section operates as a fiber Bragg grating DFB-DBR interactive laser upon sufficient pumping energy. The resulting fiber Bragg grating DFB-DBR interactive laser can be appropriately connected to pumping laser sources and WDM couplers to create fiber laser sources which are particularly adaptable to fiberoptic networks, particularly WDM and DWDM networks.

Abstract: An improved polarization beam splitter formed by a collimator and two similarly shaped, birefringent crystal prisms is provided. The light from the collimator is incident upon the first face of the first birefringent crystal prism which also has second and third faces. The collimated light is incident upon the second face at an angle .phi. with respect to a line normal to the second face so that light polarized perpendicular to a plane of incidence upon the second face is reflected toward the third face and light polarized in the plane of incidence is refracted at the second face. The second birefringent crystal prism has a second face parallel to, and in close proximity with, the second face of the first birefringent prism so that light refracted at the second face of said first prism is refracted at the second face of the second prism and into the second prism.

Abstract: The present invention provides for an improved package for a laser diode. The package has portions of its inner surfaces covered with a non-reflecting material, such as simple black paint, non-reflective metals or specific anti-reflection coatings. Such non-reflecting materials surprisingly enhances the performance of packaged laser diodes used as pumping lasers for fiber amplifiers, for example.

Abstract: Optical filters, filter systems, and methods for filtering optical signals transmitted along optical fibers provide enhanced filter performance by combining the capabilities of different types of filters particularly for dense wavelength division multiplexed systems. More specifically, the spectral skirt or transition wavelength range between a pass band wavelength range and a blocked wavelength range of a thin film pass band or dichroic filter is enhanced by arranging the thin film filter in series with one or more Fiber Bragg Gratings. The Fiber Bragg Gratings will generally reflect a portion of the signal within the spectral skirt or transition wavelength range of the thin film filter.

Abstract: A high-linearity light source comprising a first semiconductor diode (e.g., a light-source diode such as a laser diode or a light-emitting diode, or a light-receiving diode such as a photodetector) and a nonlinearity compensation network with a second, compensation, semiconductor diode is provided. The first and second diodes are connected in an antiparallel configuration with either an A.C. signal source (for light emission) or a load (for light receiving) and in separated D.C. bias paths.By varying the relative biasing of the diodes (e.g., using a variable resistor in series with a diode), the capacitance of the combination of diodes cancels, and the linearity of the system improves. With a properly biased compensation diode the even-order nonlinearity distortion can be cancelled completely.

Abstract: Optic switches manipulate an optical signal that has been expanded by a collimating lens. Switching is effected by introducing a prism between collimating lenses to redirect the optical signal to an alternative lens. The prism preferably has a cross-section defining a parallelogram, so that the optical signal is reflected twice within the prism to minimize cross-sectional distortion and avoid spectral effects. A circuit provides feedback on the actual position of the relay and prism for fault detection and diagnosis.

Abstract: A laser diode package assembly is described. Besides a laser diode, the package assembly has an optical fiber section having an end located to receive the light output from the laser diode. The optical fiber section also has a fiber grating designed to operate as a bandpass filter. The fiber grating inside the package assembly not only narrows the output wavelength from the laser diode, but also increases the lifetime of the laser diode.

Abstract: An improved polarization beam splitter formed by a collimator and two similarly shaped, birefringent crystal prisms is provided. The light from the collimator is incident upon the first face of the first birefringent crystal prism which also has second and third faces. The collimated light is incident upon the second face at an angle .phi. with respect to a line normal to the second face so that light polarized perpendicular to a plane of incidence upon the second face is reflected toward the third face and light polarized in the plane of incidence is refracted at the second face. The second birefringent crystal prism has a second face parallel to, and in close proximity with, the second face of the first birefringent prism so that light refracted at the second face of said first prism is refracted at the second face of the second prism and into the second prism.

Abstract: The present invention provides for multiple wavelength laser sources. The laser source has a pumping laser generating output at a wavelength, typically below 1500 nm, and a plurality of DBR fiber lasers or DFB fiber lasers, each having an output which is centered at a selected wavelength in the 1550 nm range. The fiber lasers are connected to the pumping laser such that the output light from said first pumping laser provides lasing energy for each of said fiber lasers. The fiber lasers may be connected serially or in series to each other. An optical fiber amplifier may be connected to the output of the serially-connected fiber lasers, or to the output of each one of the parallel-connected fiber lasers, to amplify the output from the fiber lasers so that the pumping laser provides energy for both the fiber lasers and the optical fiber amplifier.

Abstract: Arrangements for high output power laser sources and optical fiber amplifiers are disclosed. In one arrangement, an optical fiber section which is doped with erbium, is coupled with one or two mirror elements, such as fiber Bragg gratings, to form a DBR or DFB fiber laser. The optical fiber section receives energy at one end from a pumping laser and lases at one or more selected wavelengths. This output light, along with energy from the pumping laser, is transmitted through the second end of the optical fiber section to an erbium-doped fiber amplifier, which boosts the laser output even higher. The gain of the optical fiber section may be further increased by co-doping the section with erbium and ytterbium. With co-doped optical fiber sections, high power output fiber optical amplifiers and laser sources, in the form of DBR and DFB fiber lasers, which can accept the pumping energies of a plurality of pumping lasers, can be created with properly selected WDM coupler and WDM coupler/isolator devices.

Abstract: A fiberoptic coupler capable of many functions is presented. The basic fiberoptic coupler has a first sleeve, a second sleeve, a first collimating GRIN or conventional lens, and a second collimating GRIN or conventional lens. The first sleeve holds end sections of two or more input optical fibers along the longitudinal axis of the sleeve. The second sleeve holds an end section of at least one output optical fiber. The end face of the second sleeve faces the first sleeve end face. The first collimating GRIN or conventional lens in front of the first sleeve end face collimates light signals from the input optical fibers and the second collimating GRIN or conventional lens in front of the second sleeve end face focusses light signals from at least one of the input optical fibers into the single output fiber, or at least one of the output optical fibers. With only one output fiber the coupler operates as a combiner.