Abstract:
Stabilization of an oscillator, particularly an RF oscillator, is achieved by an arrangement employing a fiber optic delay line. The delay line has a Q defined by the relationship Q=2.pi.f.tau., where f is the oscillator operation frequency and .tau. is the length of the delay line. Opto/electronic and electro optic transducers are coupled between the electrical oscillator circuitry and the optical delay line for interfacing the electrical section of the RF oscillator with its optical section. This optic delay line may be configured as a single optical fiber where a single output frequency is desired, or it may be configured of a plurality of optical fibers of respectively different lengths, where plural output frequencies are to be produced.
Abstract:
A fiber optic repeater includes a photodetector stage, an amplification and pulse sharpening stage and a driven stage for an injection laser diode, the three stages being made up of only three MESFETs, preferably of the GaAs type and each stage being similar to the other stages in configuration so as to lend itself to MSI or LSI fabrication of a very simplified and reliable microwave frequency optical repeater.
Abstract:
A coupler for transferring signals from a first group of single optical fibers to a second group of single optical fibers. The coupler provided for this purpose is a directional star coupler which is constructed so as to eliminate any need for the employment of a mixing chamber. A covering, or cladding, generally covers each optical fiber in order to prevent light from being emitted through the circumferential surface of such fiber. At an end portion of each of the fibers of both the first and second groups, the cladding is treated so as to allow light to be emitted from the circumferential surface of such portion. The end portions of the fibers of the first group are fed through an opening at one side of a coupling chamber. The end portions of the fibers of the second group are fed through another opening within the coupling chamber. The first and second groups of fibers are arranged within the chamber so that their end faces are in abutment with each other. In this manner, signals transmitted along any of the fibers of the first group are transferred to all of the fibers of the second group.
Abstract:
The excitation or coupling of microwave integrated circuits to a cavity or resonator is effected by a substrate forming part of the wall of the cavity and on which there is disposed a microstrip or a strip or a slot line.
Abstract:
Miniature optical devices, including circulator array devices, are fabricated using thin film coating technology. A typical optical device includes two refraction elements arranged opposite each other along a propagation axis and coupled on opposite ends to first and second polarization orientation elements with first and second PBS elements are coupled to the first and second polarization orientation elements, respectively. The refraction elements include complementary Wollaston Prism elements or Rochon Prism elements. Each polarization orientation element includes a Faraday rotator element, and in some embodiments, a half-wave plate formed using thin film coating techniques. The Faraday rotator elements are periodically poled in some embodiments using selective poling techniques to create oppositely oriented magnetic domains so that polarization rotations of 45 degrees in both clockwise and counter-clockwise directions can be simultaneously achieved on the same magnetic garnet. Periodically etched half-wave plates are used in some embodiments.
Abstract:
An EDFA with integrated input and output modules is presented. The integrated input module has a packaged pump laser diode mounted to the metal EDFA package to provide a heat sink for the pump laser diode which sends the pump laser light over a optical fiber section connected to the amplifying erbium-doped optical fiber section. The fiber section is formed from an optical fiber which better matches the transmission modes in the erbium-doped optical fiber section and has an end subsection of the single mode fiber for a larger numerical aperture. Collimating lenses also increase the coupling efficiency of the laser diode to the erbium-doped fiber section. The integrated output module has a photodiode with a tap filter to monitor the output power of the EDFA, an optical isolator to prevent interference in the erbium-doped optical fiber section. With a twin optical isolator, the integrated input and output modules can be arranged in different ways and combinations with the erbium-doped optical fiber section. The resulting EDFAs can be manufactured relatively inexpensively into an very small packages compared to current EDFA packages.
Abstract:
A miniature WDM add/drop multiplexer and its manufacture is described. The device has a plurality of wavelength-dependent filters in the form of thin-film filters mounted to a core frame with the end sections of the input/output optical fiber and other optical fibers associated with each of the filters. The stresses associated with the filters are accounted for. The core frame is sealed, together with the overall package assembly, to provide for long-term reliability of the device. The described device and method of manufacture is also generally applicable to WDM multiplexers and demultiplexers.
Abstract:
A polarization element and a polarization-sensitive optical isolator are integrated to form an integrated VOA. A preferred embodiment uses a liquid crystal cell as the polarization element to which is attached an optical isolator core of a first polarizer, Faraday rotator, and second polarizer. Voltage on the liquid crystal cell electrodes controls the amount of polarized light from the liquid crystal cell passing through the first polarizer and light in the opposite direction is blocked. The integrated VOA can be mounted within a laser device package so that the power of the source laser diode on the output fiber can be controlled and yet the laser diode is protected from light undesirably entering laser device package through the output fiber.
Abstract:
A temperature compensation circuit arrangement for liquid crystal cells in optical devices is presented. In an optical device, a liquid crystal cell typically manipulates the optical signals according to an output optical property, such as attenuation, responsive to an AC voltage source electrical signal. A feedback circuit arrangement is connected to the liquid crystal cell and controls the current through the liquid crystal cell with respect to temperature by a predetermined control equations for the output optical property so that the device manipulates the optical signals independently of temperature. The current follows the control equations, which are empirically determined with respect to temperature for one equation.
Abstract:
The invention provides improved optical devices, systems, and methods for controllably varying an optical characteristic of an optical signal, particularly for filtering and generating optical signals about a narrow tunable central wavelength. Thin film multi-cavity Fabry-Perot bandpass filters have film thicknesses which vary so as to vary the center wavelength of the filter's pass range. Novel micro lenses and lens arrangements avoid transmission of optical signals through a large area of the optical filter, which would widen the effective pass bandwidth and reduce coupling efficiency. These bandpass filtering techniques can be used in an external cavity laser system to provide a tunable laser source.