Monday, 17 September 2012

Inertial Sensors and Systems - Symposium Gyro Technology 2012

HiBi Single Polarizing HB-Z Zing™ Fibers for Fiber Optic Gyroscopes

0930 hrs Day 2: Wednesday 19 September 2012

Jose Alvarez will be discussing the use of HB-Z Zing™ fibers in FOGs in the second of our two papers at this Show.  Introduced in 2010, continual development now enables us to offer two new variants for operating at around 830 nm and 1310 nm, in addition to the original HB1060Z . 

Over the last few years the Inertial Navigation System (INS) industry has experienced an increasing demand in the accuracy of the gyroscopes for new military, space and civil applications. In this sense, setting and controlling the polarization state of the light launched into the fiber coil is a critical issue when designing a high precision Fiber Optic Gyroscope (FOG).

Traditionally, LiNbO3 multi-funtional integrated optical chips (MIOCs) have included the polarizing functionality in the gyro along with the splitter and the modulator, with different results in performance, cost and resilience.  The complexity of including the MIOC in the FOG design, and its high impact in the total cost of the gyroscopes, have created many problems to the FOG manufacturers. To support the industry, Fibercore have designed a new range of polarizing Zing™ fibers that will bring an all-fiber passive solution to this problem in terms of reduced cost, compact packaging, low insertion losses, power consumption, reliability, etc. 

A polarizing fiber guides the light in just one axis of the transmitted mode, cancelling the orthogonal degenerated mode by means of bending losses due to its extremely high birefingence levels.  This high birefringence (represented by a beat-length of about 0.6 mm @ 633 nm) creates a different refractive index and therefore a different propagation constant for the light traveling on both fast (lower refractive index) and slow (higher refractive index) axis. Therefore the bend edge of both axes will be clearly separated and, at some point, the fiber will guide the light in just one of the axes allowing for a stable single polarizing window of 100 nm - 200 nm with higher than 30 dB PER levels. To encourage this behaviour, the fiber will operate far away from the cut-off region and the initial NA of the fiber will be as low as possible so the polarizing effect is much more noticeable.

A theorectical explanation, based on the bending loss equation, of the basic operation and design principles of these fibers will be given in the paper.  The benefits of an all-fiber solution over other alternative technologies will be discussed along with significant experimental results showing the performance of the Zing™ fibers under different deployment and system conditions.


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