Reconfigurable ultra-broadband mode converter based on a two-mode fiber with pressure-loaded phase-shifted long-period alloyed waveguide grating

Abstract

We present a reconfigurable ultra-broadband mode converter, which consists of a two-mode fiber (TMF) and pressure-loaded phase-shifted long-period alloyed waveguide grating. We design and fabricate the long-period alloyed waveguide gratings (LPAWG) with SU-8, chromium, and titanium via the photo-lithography and electric beam evaporation technique. With the help of the pressure loaded or released from the LPAWG onto the TMF, the device can realize reconfigurable mode conversion between the LP01 mode and the LP11 mode in the TMF, which is weak sensitive to the state of polarization. The mode conversion efficiency larger than 10 dB can be achieved with operation wavelength range of about 105 nm, which ranges from 1501.9 nm to 1606.7 nm. The proposed device can be further used in the large bandwidth mode division multiplexing (MDM) transmission and optical fiber sensing system based on few-mode fibers.

Mechanically Induced Long-Period Fiber Gratings and Applications

“…LPFGs can be formed through many techniques, such as laser-induced refractive index change [29][30][31], laser-induced structural change [32], and mechanically induced refractive index/structural change [33], etc. Among them, the catalog of the mechanically induced, for which the main principle is the refractive index modulation caused by the elastic-optical effect of optical fiber, can be mainly divided into two kinds.…”

Design of a Broadband Integrated Mode Converter Based on Non-Uniform Binary Long-Period Grating by Direct Multiparameter Optimization

“…purposes, depending on the coupling type [1,2]. In particular, LPGs can be used as mode converters [3][4][5][6][7][8][9][10][11][12][13][14] when coupling occurs between different copropagating core modes. Due to the resonant nature of the couplings, LPGs typically have a narrow spectral bandwidth, which is an important limitation in many practical applications.…”

“…Due to the resonant nature of the couplings, LPGs typically have a narrow spectral bandwidth, which is an important limitation in many practical applications. To overcome this problem, several methods for broadening and shaping the spectral characteristics of LPGs have been proposed, including chirping the grating period [4,15,16], shifting the phase of different grating sections [5,6,17], fabricating multisection phase-shifted gratings with proper period variation within each section [6,18], apodized phase-shifted gratings [19], and exploiting a dual resonance coupling effect [7,8,20]. Using such solutions, a significant broadening of the spectral bandwidth of LPG-based devices has already been experimentally and theoretically demonstrated.…”

“…Using such solutions, a significant broadening of the spectral bandwidth of LPG-based devices has already been experimentally and theoretically demonstrated. For example, in the optical fiber LPGs, the following conversion bandwidth was obtained between LP01 and LP11 modes: 105 nm for -10 dB crosstalk (CT) level for phase-shifted LPGs [5], 145 nm (-13 dB CT) for phase-shifted chirped LPG composed of 4 segments [4], 182 nm (-10 dB CT) for cascaded lengthapodized phase shifted LPGs [6], 130 nm (-15 dB CT) for tapered dual-resonance LPG [7], and 118 nm (-15 dB CT) for dual-resonance LPG [8].…”