Backscatter Compensation in IFOG Based Inertial Measurement Units With Polymer Phase Modulators

• Published in: Journal of lightwave technology Vol. 27; no. 6; pp. 806 - 813
• Main Authors: Sanghadasa, M., Ashley, P.R., Lindsay, G.A., Bramson, M.D., Tawney, J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 15-03-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Backscatter; Backscattering; Circuit properties; Costs; Design engineering; Electric, optical and optoelectronic circuits; Electro-optic polymers; Electronics; Exact sciences and technology; gyroscopes; Inertial; Information, signal and communications theory; integrated optics devices; Integrated optics. Optical fibers and wave guides; Interference; Low voltage; Measurement units; Miniaturization; Modulation, demodulation; Modulators; Navigation; Optical and optoelectronic circuits; Optical data processing; Optical losses; Optical polymers; Optical waveguides; Optoelectronic devices; Phase modulation; polymer waveguides; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Signal and communications theory; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Waveguides; Integrated optics; Electro-optic polymers; Noise reduction; integrated optics devices; Backscattering; Wave propagation; Guidance system; Electrooptical effect; Wave generation; Cost lowering; Backscatter; polymer waveguides; Navigation system; Phase modulation; Measurement sensor; Phase modulator; Guided wave; Electrooptical device; Polymer; Compact design; Waveguide; gyroscopes; Interference suppression; Manufacturing process; Insertion loss; Signal processing; Active component; Gyroscope; Miniaturization
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2008.928915

Precision guidance in navigation systems requires highly accurate, compact, and low cost inertial measurement units (IMUs). The key active guided-wave component of the IMU is the phase modulator. In our approach, electro-optic polymers have been utilized in fabricating low loss phase modulators with low half-wave drive voltage using advanced hybrid waveguide fabrication processes and novel optical integration techniques. However, the interference between the primary wave and the backscatter waves generated by the phase modulator and/or the interference between the two counter-propagating backscatter waves at the detector of the IMU has been a major source of error in this approach. A novel technique was introduced in assessing the error caused by backscatter and an offset waveguide design was developed to suppress the interference of backscatter light. The novel design not only preserved the miniaturization, but also improved the insertion loss with the use of a shorter waveguide. The gyro level tests performed with the backscatter compensated modulators showed about 5 times improvement of the average bias uncertainty over gyros integrated with a standard symmetric phase modulator.