LP01/LP11 dual-mode and dual-polarisation CO-OFDM transmission on two-mode fibre

Abstract

Reported are the transmission characteristics of a dual-mode and dualpolarisation coherent optical orthogonal frequency-division multiplexed (CO-OFDM) system where a simple grating-based LP 01 -LP 11 mode converter is used for mode selective detection. Compared to the LP 01 mode component, the LP 11 mode shows a penalty of 2 and 3.8 dB for the two polarisations after 4.5 km of two-mode fibre at 36 Gbit/s. Potential for broadband operation is also confirmed.Introduction: The capacity limitation of the singlemode fibre (SMF) due to fibre nonlinearity [1] has created interest in new fibre designs with multiple cores or spatial modes. Spatial mode diversity in multimode or few-mode fibre (MMF/FMF) can multiply the absolute spectral efficiency (SE) and enhance data rate [2]. Proof-of-principle demonstrations have been reported in MMF [3], but MMF has the disadvantage of having difficulty to selectively couple to a fibre mode, causing adverse effects from modal dispersion. Compared to MMF, FMF such as two-mode fibre (TMF) has the advantage of easier mode selective coupling of SMF components to any of the orthogonal propagation modes [4 -6]. Mode mixing among the LP 01 and two orthogonal LP 11 modes in TMF is shown to be reversible by complex channel equalising filters in [4]. However, a TMF design with sufficient modal dispersion prevents inter-modal mixing [7], enabling independent transmission paths over the LP 01 and LP 11 modes. This concept of LP 01 /LP 11 dual-mode transmission is demonstrated with a 2 × 10 Gbit/s on -off keying optical signal using an LP 01 -LP 11 mode coupler in [5], but in a single polarisation and at 1080 nm wavelength. We have recently demonstrated the feasibility of standard C-band, dual-polarisation, LP 01 /LP 11 dual-mode transmission by a coherent optical orthogonal frequency-division multiplexing (CO-OFDM) signal, using a grating-based LP 01 -LP 11 mode converter at the mode-selective element [6]. In this Letter, we evaluate the potential for broadband transmission in the proposed scheme. We also report the measured OSNR sensitivities for both LP 01 and LP 11 modes and both polarisations.

Accurate Estimate of Some Propagation Characteristics for the First Higher Order Mode in Graded Index Fiber with Simple Analytic Chebyshev Method

“…and a 1 can be set arbitrarily. However, in case of SIF, ψ is Bessel function J 1 (UR) in core and K 1 (WR) in cladding; also, 1 …”

“…Transmission characteristics of dual mode and dual polarization of CO-OFDM system are studied using LP 01 -LP 11 modes [1]. LP 11 mode has also been used in fiber sensors to separate temperature variation from longitudinal strain by intermodal interference [2].…”

Characterization of stimulated Brillouin scattering in a few-mode fiber

“…The intermodal SBS is observed in each pump-probe pair of different modes, and the Brillouin gain is measured to be within 14%-45% of that of the SBS between the LP 01 modes. The SBS threshold of each LP mode in the FMF is also evaluated.As space-division multiplexing (SDM) emerges as a promising technology for increasing the capacity of communication systems, few-mode fiber (FMF) is attracting considerable attention as a new platform for realizing multiple parallel channels [1,2]. Stimulated Brillouin scattering (SBS) is a dominant nonlinear effect in optical fibers with the lowest threshold, and its characterization has provided useful information for designing and enhancing optical fibers and sensors [3,4].…”

Broadband mode division multiplexer using all-fiber mode selective couplers

“…The only remaining physical dimension not fully utilized is considered to be the space dimension in a strand of optical fiber [2]. The two popular approaches to the space division multiplexing (SDM) that are intensively investigated are multi-core fiber (MCF) [3][4][5] and mode division multiplexing (MDM) [6][7][8]. The MCF approach uses optical fibers with multiple single-mode cores and the MDM approach uses few mode optical fiber (FMF) with a core that guides several spatial/polarization modes [9,10].…”