Carl A. Villarruel

Fiber-optic gyroscope with polarization-holding fiber.

A fiber gyroscope is reported that uses polarization-holding fiber in the coil, the phase modulator, and the coupler. The random-drift coefficient, calculated from rms noise levels, was 8.10−4deg/h, within a factor of 2 of an experimentally determined quantum and thermal limit. White-noise behavior was observed for integration time constants from 1 to 40 sec. Device characteristics and performance are presented.

Output characteristics of diode pumped fiber ASE sources

High power amplified spontaneous emission (ASE) from multicore Nd:fibers pumped by laser diode arrays is investigated experimentally and theoretically. Particular examination is made of threshold conditions at which lasing occurs. A model is presented which describes output power for arbitrary end reflectors. Experimental measurements of lasing threshold reflectivity versus pump power are made and are shown to deviate from the usual laser threshold condition at high pump powers. It is demonstrated that feedback from Rayleigh backscattering can be sufficient to drive the ASE source above lasing threshold in certain configurations. >

Internal rotation of the birefringence axes in polarization-holding fibers

An internal rotation of the birefringence axes has been measured in a variety of polarization-holding fibers. The rotation of the axes causes coupling of the major-field components of the fundamental modes, which limits the polarization-extinction ratio in short lengths of birefringent fibers to -45 dB in some cases. A practical consequence of the rotation of the axes is a reduction of the polarization-holding ability of devices such as fiber couplers that are made with these fibers.

All-fiber gyroscope with polarization-holding fiber.

An all-fiber gyroscope is reported that is constructed entirely of polarization-holding fiber. The random-drift coefficient was 5 x 10(-3) deg/ radicalh. Gyro bias drift is shown to be stable over periods of hundreds of hours. Device construction details and some thermal dependence of components are given.

Loss mechanisms in single-mode fiber tapers

The onset of transmission loss in four single-mode tapers is shown to coincide with the taper slope exceeding the critical slope angle at which fundamental mode cutoff occurs. This implies that the primary loss mechanism in single-mode fiber tapers is cutoff of the fundamental mode from the core. A secondary loss mechanism of coupling to the modes of a coaxial outer waveguide is also observed and modeled. Implications for fused fiber couplers are discussed.

Reproducible fabrication method for polarization preserving single-mode fiber couplers

The adaptation of the biconically-tapered-fused (BTF) fiber coupler fabrication approach to polarization preserving fiber couplers is reported. Two practical methods for identifying and aligning the birefringent axes of the fibers forming the coupler are described. The fabrication approaches are highly reproducible and the 3-dB couplers fabricated exhibit less than 1.0-dB insertion loss, controllable splitting ratio, and an average polarization extinction ratio of 15 to 20 dB. >

9 × 9 single-mode fiber-optic star couplers

A 9 x 9 single-mode fiber-optic star coupler that displays an excess loss of 1.46 dB and a uniformity of 1.50 dB is described. Design and fabrication are discussed, and performance data are presented.

Multichannel fiber-optic magnetometer system for undersea measurements

We have designed, fabricated, and operated an undersea array of eight fiber-optic vector magnetometers. Each magnetometer consists of three magnetostrictive transducers aligned on orthogonal axes and incorporated in a single Michelson interferometer. During undersea operation, each interferometer exhibited less than 1 /spl mu/rad//spl radic/ Hz phase noise, and the self-noise of each magnetic transducer was less than 0.2 nT//spl radic/ Hz at 0.1 Hz. We discuss the design and performance of the optical system including noise mechanisms. We present the results of magnetic measurements of the geomagnetic field and the magnetic tracking of ships. >

A simple high-speed high-output voltage digital receiver

We present measurements of a simple photoreceiver capable of generating 2.0 V at 19-Gb/s nonreturn-to-zero (NRZ), and 2.0 and 3.0 V at 24 and 10-Gb/s return-to-zero (RZ), respectively, directly from a p-i-n photodiode. Thus, this photoreceiver generates signal levels compatible with high-speed logic, clock recovery, and/or modulation with low-V/sub /spl pi// LiNbO/sub 3/ modulators without the need for electrical postdetection amplification. The bit-error ratio (BER) is not compromised with this approach since this receiver generates clean eye diagrams with a BER of 10/sup -9/ with -30-dBm input at 10 Gb/s.

Continuously-tunable microwave photonic true-time-delay based on a fiber-coupled beam deflector and diffraction grating.

This paper reports the demonstration of a continuously-tunable true-time delay line for microwave photonics and optical communications capable of high-resolution phase control throughout the 1-100 GHz modulation range. A fiber-coupled device is demonstrated with 75 ps of continuous delay tuning range, 3 dB optical insertion loss, and minimal RF amplitude and phase variation over the 4-18 GHz band. Measured delay ripple was less than 0.2 ps. Theoretical analysis is also presented which indicates scalability to delay tuning ranges over 1000 ps and modulation bandwidths over 10 THz.