Fiber mode coupling in transmissive and reflective tilted fiber gratings

Abstract

Whereas core-mode reflection and core-mode-to-radiation-mode coupling in tilted fiber Bragg gratings is well understood, as is coupling between a core mode and higher-order core and cladding modes in untilted gratings, here we analyze in detail the coupling among core modes and cladding modes in reflective and transmissive tilted fiber gratings. We show that strong coupling between an LP(01) core mode and the exact (1m) cladding modes occurs in a transmissive tilted grating for nearly any tilt angle except angles close to 90 degrees, whereas the LP(01)-to-(lm) cladding mode coupling (l not equal 1) is appreciable only for tilt angles just below 90 degrees (approximately 88 degrees). In a reflective grating, strong coupling between the LP(01) core mode and the exact (1m) cladding modes occurs only for angles less than approximately 5 degrees, whereas coupling to (1m) cladding modes for m > 1 occurs only for angles greater than approximately 5 degrees. Coupling among bound core modes exhibits a similar behavior, except that in general the coupling is stronger. Experimentally we show coupling to both higher-order bound core modes and cladding modes in a transmissive tilted grating at visible and near-infrared wavelengths.

A novel mode add/drop multiplexer based on two parallel combinative long period fiber gratings

“…In this paper, we choose the second order cladding mode as the medium mode, in view of the grating in SMF is tilted long period fiber grating (TLPFG) (Lee and Erdogan 2000). In order to make the coupling coefficients large enough, the tilted angel is about 87° (Lee and Erdogan 2000).…”

“…In order to make the coupling coefficients large enough, the tilted angel is about 87° (Lee and Erdogan 2000). When the tilted angel is 87°, we calculate the coupling coefficients between the fundamental mode LP 01 and all the second order cladding modes, which are demonstrated in Fig.…”

Experimental and theoretical characterization of optical signal out-coupling through V-grooved optical fiber cladding

“…[7][8][9][10] The coupling between the modes is maximized if one of the following phase-matching conditions is satisfied: …”

Analysis of coupling from core mode to counter-propagating radiation modes in tilted fiber Bragg gratings

“…For the VCM, the waveguide boundary is neglected, and this approach is used mainly to calculate the azimuthal energy distribution of radiation modes in the near and far fields [16][17][18]. For the CMT approach, it features clear physical concepts and is an effective method for analyzing interactions between different modes in optical fiber gratings [19][20][21][22]. Because the index difference at the waveguide boundary is considered, the CMT is the more rigorous one of the two approaches, and is convenient for simulating the loss spectrum.…”