Pseudo-random-bit-sequence phase modulation for reduced errors in a fiber optic gyroscope.
Low noise and drift in a laser-driven fiber optic gyroscope (FOG) are demonstrated by interrogating the sensor with a low-coherence laser. The laser coherence was reduced by broadening its optical spectrum using an external electro-optic phase modulator driven by either a sinusoidal or a pseudo-random bit sequence (PRBS) waveform. The noise reduction measured in a FOG driven by a modulated laser agrees with the calculations based on the broadened laser spectrum. Using PRBS modulation, the linewidth of a laser was broadened from 10 MHz to more than 10 GHz, leading to a measured FOG noise of only 0.00073  deg/√h and a drift of 0.023  deg/h. To the best of our knowledge, these are the lowest noise and drift reported in a laser-driven FOG, and this noise is below the requirement for the inertial navigation of aircraft.
Hiding single photons with spread spectrum technology.
We describe a proof-of-principal experiment demonstrating the use of spread spectrum technology at the single photon level. We show how single photons with a prescribed temporal shape, in the presence of interfering noise, may be hidden and recovered.
Robustly single mode hollow core photonic bandgap fiber.
We report the fabrication of a novel type of hollow core photonic bandgap fiber (PBGF) with a small core formed by 3 omitted unit cells in a triangular array of holes. The transmission properties of fibers designed for operation at 1500nm wavelength are investigated both experimentally and through extensive modeling. The novel PBGF structure provides robust single mode guidance and is of particular interest for device applications which require low index bandgap guidance and short device lengths.