High Stability Er-Doped Superfluorescent Fiber Source Improved by Incorporating Bandpass Filter

Abstract

A Faraday rotator mirror incorporating a Gaussian bandpass filter was used as the reflected end of an Er-doped superfluorescent fiber source to improve its mean wavelength thermal stability. Several different filters were modeled in this fiber source system, and the optimal central wavelength was chosen to be 1558 nm with the bandwidth of 15 nm. With a Faraday rotator mirror incorporating such a filter in an Er-doped fiber source, the mean wavelength variation was measured to be 8 ppm from 40 C to 60 C. The bandwidth reached 16 nm. The pump power was 70 mW at 974.2 nm and the output power reached 18 mW with 6-m Er-doped fiber.Index Terms-Bandpass filter, superfluorescent fiber source. E RBIUM (Er)-doped superfluorescent fiber sources (SFSs) have been extensively studied in interferometric fiber-optic gyroscopes (IFOGs) [1]- [6]. The gyroscope scale factor depends on the optical mean wavelength of gyro system signals, and the rotation rate can only be measured accurately if this mean wavelength is precisely known. A high-grade IFOG requires that its SFS has a mean wavelength stability in parts per million (ppm) [3], which is primarily affected by the pump power, pump wavelength, the pump state of polarization, the feedback power and the Er-doped fiber (EDF) temperature [2]. The influences of the former four factors can be reduced to ppm level by selecting optimal pump parameters [1], [2], [4], stabilizing pump laser and using high-performance fiber optic components [2], [5]. The main instability source is from the EDF-temperature. It can modify the emission and absorption cross-sections of erbium ions, inducing a drift in the mean wavelength. Values of the thermal coefficient ranging from to ppm C have been reported in different SFS configurations [1], [4], [6]. Even though a temperature controller can be applied on EDF, it is quite power consuming, making the system more complicated, especially when the source works in broad temperature range (over 100 degrees). Different in-line fiber optic filters have also been reported to compensate the mean wavelength drift, such as long period fiber gratings [7], Bragg fiber gratings [8], [9], and photonic bandgap fibers [10]. However, to my knowledge, matched fiber filters are quite hard to be accurately fabricated to compensate a specific fiber source, limiting their practical applications.Fig. 1. DPBS Er-doped superfluorescent fiber source configuration.In this letter, a Faraday rotator mirror (FRM) incorporating a Gaussian bandpass filter was used as the reflected end in a double-pass backward-signal (DPBS) Er-doped SFS. The central wavelength of the bandpass filter was selected to be around 1558 nm corresponding to one emission peak of Er ions. Its bandwidth was set to be 15 nm. The reflected signals were filtered out to force the emission spectrum fixed around the 1558 nm emission peak, stabilizing the mean wavelength variations with temperature. After incorporating such a device into the SFS, the mean wavelength variation can reach less than 8 ppm for the temperature...

Stabilisation of central wavelength of erbium‐doped fibre source as part of high‐accuracy fibre optic gyroscopes

“…The long-period fibre grating [12][13][14], the fibre Bragg grating [15][16][17], the unpumped EDF [18][19][20], and thin-film filters [15,16,21] are implemented as temperaturecompensating spectral filters. However, in many cases, it is necessary to create unique spectral filters and choose the optimal parameters (the optimal length of the EDF and/or the optic power of the pump laser) for each optic scheme of the EDFS [5,17,[22][23][24][25].…”

Stabilisation of central wavelength of erbium‐doped fibre source as part of high‐accuracy FOG

“…The long-period fibre grating [12][13][14], the fibre Bragg grating [15][16][17], the unpumped EDF [18][19][20], and thin-film filters [15,16,21] are implemented as temperature-compensating spectral filters. However, in many cases, it is necessary to create unique spectral filters and choose the optimal parameters (the optimal length of the EDF and/or the optic power of the pump laser) for each optic scheme of the EDFS [6,17,[22][23][24][25].…”

High-stable Erbium superluminescent fiber optical sources creation methods

“…Подробно метод вариаций Аллана на примере анализа погрешностей микромеханических гироскопов описан в работе [48]. Эффективным вариантом является построение видоизмененных двух-проходных оптических схем накачки легированного эрбием волокна с применением полосовых фильтров, комбинированных с зеркалом Фарадея [49][50][51]. Например, применение двухкаскадной схемы источника с использованием для каждого каскада как общего диода накачки, так и разных, с разными длинами волн (980 нм и 1480 нм), позволяет добиться более широкого и гладкого спектра [52,53].…”

“…В результате проведенного обзора стало очевидно, что тема повышения стабильности эрбиевых суперлюминисцентных волоконных источников оптического излучения, в особенности для повышения точностных характеристик волоконно-оптических гироскопов, очень актуальна [2, 19,23,39,49,54]. Были определены основные тенденции развития эрбиевых суперлюминисцентных волоконных источни-ков оптического излучения, как в общем, так и в частности, для применения в волоконно-оптических гироскопах повышенной точности.…”