Effect of gain-dependent phase shift for tunable abrupt-tapered Mach–Zehnder interferometers

Abstract

A differential gain-dependent phase shift between the core mode and the cladding mode can be all-optically tuned by a cw 975 nm pump light for Mach-Zehnder interferometers using two abrupt fiber tapers in a 1.2-cm-long highly Er/Yb codoped fiber. The highly doped fiber has large absorption and emission cross sections to efficiently introduce the phase shift when the inversion rate is changed by varying the pump power. The first abrupt taper converts part of core mode into the cladding mode, while the second abrupt taper recombines both modes to interfere after propagating for a length of a few millimeters.

High extinction-ratio dual thin-taper fiber interferometer fabricated by arc-discharge and its performance as sensors

“…Especially, they have wide applications as fiber filters and sensors [1][2][3][4][5][6][7][8][9][10][11][12]. As we all know, the primary requirement for the fiber filter is its high extinction ratio (ER).…”

“…Generally, the common thin-taper SMF based MI is below 5 dB due to the unoptimized waist diameter of about 65 mm [10]. A high ER thintaper MI can be fabricated on the Er-Yb co-doped fiber (EYDF) with 50-mm waist diameter since the fiber has a high index contrast between the cladding and highly phosphorous doped core [11,12]. In addition, generally, there are two heating techniques for fabricating the dual thin-taper MIs, point flame and discharge.…”

In-line high sensitivity tapered-fiber Mach-Zehnder interferometer for aerospace sensing applications

“…In aerospace photonic applications, fiber sensors with compact size, low cost, simple structure, high sensitivity, high environment stability, and multiple measurands are highly appreciated [1][2][3][4]. Usually, fiber-optic sensors are based on fiber Bragg gratings, gyroscopes, long period gratings, abrupttapered-fiber Michelson interferometers (MIs) and MachZehnder interferometers (MZIs).…”

“…The span fiber which is the un-tapered segment between two abrupt tapers plays a role as a phase shifter to generate the OPLD and the merits of using EYDF is to provide distinct OPLD between the core and cladding modes. This is ascribing to that the erbium and ytterbium ions are not easy to be diffused during high temperature heating and tapering so that the core boundary is not blurred [4]. Moreover, the resonant wavelengths can be all-optically tuned by changing the OPLD between the core and cladding modes.…”

Interferometric Interrogation of the Inclination and Displacement of Tapered Fiber Mach-Zehnder Interferometers

“…In this work, two successive abrupt tapers have been made in EYDF to obtain compact AT-MZIs for inclination and displacement sensing. The advantage of using EYDF is that the erbium and ytterbium ions in EYDF have a slow rate of diffusion during the lowtemperature (∼ 700°C) hydrogen flame tapering process [18], compared with the germanium ions. Thus, these ions serve as an effective waveguide, separating the core and the excited cladding modes distinctly to achieve the π phase shift more efficiently.…”