J. Stone

FDMA-FSK star network with a tunable optical filter demultiplexer

An optical frequency-division-multiple-access (FDMA) star network is analyzed and demonstrated experimentally using two 45-Mb/s frequency-shift-keyed (FSK) laser channels at 1.5 mu m. A tunable fiber Fabry-Perot (FFP) filter is used to select channels and convert FSK to intensity modulation for direct detection. The analysis predicts and experiment supports a minimum channel spacing of about six times bit rate B for a single FFP. These constraints are similar to those for more complex heterodyne demultiplexing. Estimates show that a network with 1000 users, independent of bit rate, is feasible with a tandem FFP. For B=1 Gb/s per channel the network capacity would be 1 Tb/s. >

Interactions of hydrogen and deuterium with silica optical fibers: A review

This paper reviews all the interactions of hydrogen and deuterium with silica-based optical fibers. Included in the discussion are H 2 overtone absorption, OH formation, increased UV and IR absorption, radiation effects on H 2 -treated fibers, the gas-in-glass laser and applications, the reduction of OH absorption by isotope exchange OH → OD and other isotope-exchange related effects, and applications of isotope exchange and substitution for diagnostic purposes. Also included is a description of common sources of H 2 in materials used in fiber and cable manufacture, and countermeasures against hydrogen generation and intrusion into the fiber.

Ultrahigh finesse fiber Fabry-Perot interferometers

Fiber Fabry-Perots have been built with a finesse of 500 and throughput of 30-40 percent. The devices are piezoelectrically scanned and operate at 1.52μm, and have free spectral ranges of 1000, 500, 333, and 250 MHz, with linewidth resolution as small as 0.5 MHz. The sources of loss which limit the attainable finesse have been identified and analyzed.

A tunable Vernier fiber Fabry-Perot filter for FDM demultiplexing and detection

An N-channel optical frequency-division multiplexing (FDM) network can be realized using frequency-shift keying (FSK) modulation and a tunable filter to select and detect the channels. A tandem arrangement of two fiber Fabry-Perot (FFP) filters is demonstrated. For FFPs with individual finesse (F) of 57 an effective finesse of 675 is obtained in a tandem arrangement. This has a capacity of N=F/3=225 channels in a frequency-division multiaccess (FDMA)-FSK network.<<ETX>>

Stress-optic effects, birefringence, and reduction of birefringence by annealing in fiber Fabry-Perot interferometers

The effects of inherent fiber birefringence, packaging stresses, and stress tuning on the behavior of a fiber Fabry-Perot interferometer are examined. A polarization doublet due to birefringence is observed. For birefringence of 1 ps/km, the doublet spacing is 40 MHz, at 1.5- mu m wavelength, independent of the FFP finesse or free spectral range, and is due mainly to the inherent fiber birefringence. It was found that annealing depressed-cladding single-mode fiber reduced the fiber birefringence, for example, from 40-80 MHz to 15-25 MHz. Where the bandpass of the FFP is greater than the birefringence doublet, this device should be polarization insensitive for most applications. >

FM and FSK response of tunable two-electrode DFB lasers and their performance with noncoherent detection

Two-electrode distributed-feedback (DFB) lasers show promise for combining high speed and frequency tunability for frequency-division-multiplexed-frequency-shift-keyed (FDM-FSK) networks. The FM and FSK responses of such lasers have been measured up to modulation frequencies of approximately 1 GHz. Using these lasers in a noncoherent detection system in which a fiber Fabry-Perot tunable optical filter converts an FSK signal into an amplitude-shift-keyed (ASK) format, a 10/sup -9/ BER was observed up to 1 Gb/s. Nonuniform FM response and consequent tone broadening of the optical FSK spectra can lead to system power penalties due to optical-filtering effects. Thus, for a given FM response, the behavior of these lasers in FSK optical systems can be projected.<<ETX>>