title: M-ary pulse-position modulation and frequency-shift keying with additional polarization/phase modulation for high-sensitivity optical transmission.
abstract: We present a new class of optical modulation formats based on the combination of m-ary pulse-position modulation (m-PPM) or m-ary frequency-shift keying (FSK) with additional polarization and/or phase modulation, which is applied on the information carrying pulses in the case of m-PPM or on the information carrying frequency carriers in the case of m-FSK. We describe the principle and implementation of this class of optical modulation formats, and formulate their theoretical receiver sensitivities in optically pre-amplified receivers. Pilot-assisted frequency-domain equalization, similar to that used in coherent optical orthogonal frequency-division multiplexing (CO-OFDM), is used for reliable channel estimation and compensation. CO-OFDM also allows m-FSK to be implemented with high spectral efficiency. As a particular format in this class, m-PPM in combination with polarization-division-multiplexed quadrature phase-shift keying (PDM-QPSK), termed as PQ-mPPM, offers superior receiver sensitivity in optically pre-amplified receivers at bit error ratios (BERs) around the thresholds of common forward-error correction codes. Record receiver sensitivities of 3.5 photons per bit (ppb) at BER = 10(-3) and 2.7 ppb at BER = 1.5 × 10(-2) are experimentally demonstrated at 2.5 Gb/s and 6.23 Gb/s using PQ-16PPM and PQ-4PPM, respectively. We further demonstrate the transmission of a 6.23-Gb/s PQ-4PPM signal over a 370-km unrepeatered ultra-large-area-fiber span with 71.7-dB total loss budget.
authors.affiliation: Bell Labs, Alcatel-Lucent, 791 Holmdel-Keyport Road, Holmdel, NJ 07733, USA. xiang.liu@alcatel-lucent.com
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.forename: S
authors.initials: S
authors.lastname: Chandrasekhar
authors.forename: T H
authors.initials: TH
authors.lastname: Wood
authors.forename: R W
authors.initials: RW
authors.lastname: Tkach
authors.forename: P J
authors.initials: PJ
authors.lastname: Winzer
authors.forename: E C
authors.initials: EC
authors.lastname: Burrows
authors.forename: A R
authors.initials: AR
authors.lastname: Chraplyvy