Temperature-Insensitive Bend Sensor Using Entirely Centered Erbium Doping in the Fiber Core

Abstract

A fiber based bend sensor using a uniquely designed Bend-Sensitive Erbium Doped Fiber (BSEDF) is proposed and demonstrated. The BSEDF has two core regions, namely an undoped outer region with a diameter of about 9.38 μm encompassing a doped, inner core region with a diameter of 4.00 μm. The doped core region has about 400 ppm of an Er2O3 dopant. Pumping the BSEDF with a conventional 980 nm laser diode gives an Amplified Spontaneous Emission (ASE) spectrum spanning from 1,510 nm to over 1,560 nm at the output power level of about −58 dBm. The ASE spectrum has a peak power of −52 dBm at a central wavelength of 1,533 nm when not spooled. Spooling the BSEDF with diameters of 10 cm to 2 cm yields decreasing peak powers from −57.0 dBm to −61.8 dBm, while the central wavelength remains unchanged. The output is highly stable over time, with a low temperature sensitivity of around ∼0.005 dBm/°C, thus allowing for the development of a highly stable sensor system based in the change of the peak power alone.

Passively mode-locked laser using an entirely centred erbium-doped fiber

“…This paper details a passively mode-locked fiber laser using a two-core optical fiber, with an undoped outer region of 9.38 μm diameter that surrounds a 4.00 μm diameter central core region doped with erbium ions at 400 ppm concentration. This optical fiber, abbreviated as TC-EDF, was developed in-house, with a designated application as a bend-sensitive active optical fiber sensor [23,24]. This same fiber was also used to demonstrate mode-locked behaviour using CNT as a saturable absorber.…”

“…TC-EDF is a new type of fiber in which the fiber core comprises two annular regions, these being a concentrated erbium-doped inner core region and a surrounding undoped outer core region. The concentrated inner core acts as the source mechanism for the amplified spontaneous emission (ASE) spectrum, and the high concentration of erbium dopant in this region results in the propagating Gaussian beam achieving maximum intensity at the core, causing excitation of erbium ions within this inner core of the fiber [23,24]. Recent experiments reported in [24] demonstrate the ASE output is relatively stable with negligible variation in output power over a measurement period of one hour.…”

Bend and refractive index sensing based on the tuning fork fiber

“…As an alternative, a simple operation, low cost, intensity-based bend/RI sensor is proposed. A number of intensity-based bend/RI sensors have been developed, for example, Ahmad et al [9] proposed a bend sensor using entirely centered Erbium doping in the fiber core whose average bending sensitivity is about 0.63 dBm/cm at curvatures ranging from 2 to 10 cm. Jeong et al [10] presented a RI sensor based on the cone-based round structure, the sensitivity of À6.9 W/RIU can be attained for measurements in the refractive index 1.33-1.38 range.…”

Investigation of Bending Sensitivity in Partially Doped Core Fiber for Sensing Applications

“…The output of the ASE is also highly stable, with no observable variation in the power output over a measurement period of one hour. The PDCF is also temperature insensitive, with only a minor variation of about ∼0.005 dBm/°C measured, thus reducing the effects of cross-sensitivity [16].…”

“…The mode field distribution for PDCF in comparison with normal doped fiber falls outside the doping area at the bending situation and suffers more due to active bending loss [15]. Temperature insensitive, with only a minor variation is the other factor of proposed fiber [16].…”