Highly efficient all-fiber tunable polarization filter using torsional acoustic wave

Abstract

We demonstrate an all-fiber tunable polarization filter with high coupling efficiency based on acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent single mode optical fiber. An over-coupling between the two polarization modes is realized over the wavelength range from 1530 nm to 1610 nm using traveling torsional acoustic wave. The measured 3-dB optical bandwidth of the filter was 4.8 nm at the wavelength around 1550 nm. The details of the filter transmission and the coupling characteristics are discussed.

Axial strain dependence of all-fiber acousto-optic tunable filters

“…In all-fiber AOTF using torsional acoustic wave, the AO coupling occurs between the two linear polarization modes of a highly birefringent (HB) fiber [3,17,18]. As in the case of the AOTF using flexural acoustic wave, the strain induces both acoustic and optical effects in the fiber, and shifts the resonant wavelength of the device.…”

“…In particular, all-fiber acousto-optic tunable filters (AOTFs) have attracted considerable interest because of their advantages such as wide and fast wavelength tuning and variable attenuation via simple electronic control [1][2][3]. Flexural and torsional acoustic waves were used in the all-fiber AOTFs.…”

Rigorous characterization of acoustic-optical interactions in silicon slot waveguides by full-vectorial finite element method

“…The particle displacement can be either longitudinal or transverse creating longitudinal, torsional, bending or flexural modes. Guided Acoustic Wave Brillouin Scattering (GAWBS), first studied in 1985 [9], where radial modes can be beneficial or detrimental [10] (as with SBS) but flexural and torsional acoustic modes have been exploited in the development of all-fiber acousto-optic tuneable filters [11]. Thus it is necessary to consider all the modes to characterize fully acousto-optic interactions.…”

Analyses of unintentional intensity modulation in all-fiber acousto-optic tunable filters

“…In particular, all-fiber acousto-optic tunable filters (AOTFs) have attracted considerable interest because of their advantages such as low insertion loss, wide and fast wavelength tuning, low polarization dependence, and variable attenuation via simple electronic control [2][3][4][5]. The all-fiber AOTFs have been demonstrated based on wavelength selective acousto-optic (AO) mode coupling by traveling flexural [2,3] or torsional acoustic wave [4][5][6]. In these devices, the acoustic waves produce the resonant coupling between two spatial modes in an optical fiber (for flexural wave) or between two polarization modes in a highly birefringent (HB) fiber (for torsional wave).…”

“…1(a), but it uses a HB fiber and two polarizers at input and output. The acoustic transducer to generate a torsional wave is composed of two pieces of PZT half-discs with opposite polling directions [5]. When a radio frequency (RF) electric signal is applied, they oscillate in opposite direction to effectively twist the horn.…”