Xu Zhang

Fiber Wireless Transmission of 8.3-Gb/s/ch QPSK-OFDM Signals in 75–110-GHz Band

In this letter, we present a scalable high-speed W-band (75-110-GHz) fiber wireless communication system. By using an optical frequency comb generator, three-channel 8.3-Gb/s/ch optical orthogonal frequency-division-multiplexing (OOFDM) baseband signals in a 15-GHz bandwidth are seamlessly translated from the optical to the wireless domain. The W-band wireless carrier is generated from heterodyne mixing the OOFDM baseband signal with a free-running laser. A W-band electronic down-converter and a digital signal processing-based receiver are used. Three-channel QPSK-OFDM W-band wireless signals are transmitted over 0.5- and 2-m air distance with and without 22.8-km single-mode fiber, respectively, with achieved performance below the forward error correction limit.

Experimental Investigations of 3-D-/4-D-CAP Modulation With Directly Modulated VCSELs

In this letter, we present experimental investigations of multidimensional multilevel carrierless amplitude phase (CAP) modulation with directly modulated vertical cavity surface-emitting lasers. The signals are transmitted over 20 km of standard single-mode fiber (SSMF). For multilevel 3-D-CAP, bit rates of 468.75 and 937.5 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For 4-D-CAP, bit rates of 416.67 and 833.3 Mb/s are achieved at two levels/dimension and four levels/dimension, respectively. For all signals, a bit-error rate below the forward error correction limit of 2.8 × 10-3 for error-free reception is achieved after 20 km of SSMF transmission. Spectral efficiencies of 2.68 and 2.08 b/s/Hz are reported for 3-D-CAP and 4-D-CAP, respectively. We believe that multidimensional modulation formats represent an attractive solution for providing more flexibility for optical fiber systems.

Experimental demonstration of adaptive digital monitoring and compensation of chromatic dispersion for coherent DP-QPSK receiver

We experimentally demonstrate a digital signal processing (DSP)-based optical performance monitoring (OPM) algorithm for in-service monitoring of chromatic dispersion (CD) in coherent transport networks. Dispersion accumulated in 40 Gbit/s QPSK signal after 80 km of fiber transmission is successfully monitored and automatically compensated without prior knowledge of fiber dispersion coefficient. Four different metrics for assessing CD mitigation are implemented and simultaneously verified proving to have high estimation accuracy. No observable penalty is measured when the monitoring module drives an adaptive digital CD equalizer.

High phase noise tolerant pilot-tone-aided DP-QPSK optical communication systems.

In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs) with approximate 300 MHz linewidth are used as transmitters and local oscillators for coherent detection of optical DP-QPSK signals. The proposed system, with central wavelength at 1540.68 nm, operates at 40 Gb/s over 80 km single mode fiber (SMF) as part of a passive optical network (PON). The deployment of pilot-tone-aided PNC algorithm guarantees a bit error rate (BER) performance below the forward error correction (FEC) threshold. Moreover, we also evaluate a novel digital signal processing (DSP) algorithm for adaptive pilot tone detection.

Single- and Multiband OFDM Photonic Wireless Links in the 75−110 GHz Band Employing Optical Combs

The photonic generation of electrical orthogonal frequency-division multiplexing (OFDM) modulated wireless signals in the 75-110 GHz band is experimentally demonstrated employing in-phase/quadrature electrooptical modulation and optical heterodyn upconversion. The wireless transmission of 16-quadrature-amplitude-modulation OFDM signals is demonstrated with a bit error rate performance within the forward error correction limits. Signals of 19.1 Gb/s in 6.3-GHz bandwidth are transmitted over up to 1.3-m wireless distance. Optical comb generation is further employed to support different channels, allowing the cost and energy efficiency of the system to be increased and supporting different users in the system. Four channels at 9.6 Gb/s/ch in 14.4-GHz bandwidth are generated and transmitted over up to 1.3-m wireless distance. The transmission of a 9.6-Gb/s single-channel signal occupying 3.2-GHz bandwidth over 22.8 km of standard single-mode fiber and 0.6 m of wireless distance is also demonstrated in the multiband system.

38.2-Gb/s optical-wireless transmission in 75–110 GHz based on electrical OFDM with optical comb expansion

We demonstrate scalable optical comb- and heterodyning-based generation, optical and 1.3-m wireless transmission, and electrical heterodyne detection of multiband OFDM up to 38.2 Gb/s occupying 14.4-GHz RF bandwidth, for high-capacity optical-wireless links in 75-110 GHz.

Performance analysis of IM, DPSK and DQPSK payload signals with frequency swept coherent detected spectral amplitude code labelling

We present the performance analysis for frequency swept coherent detection of spectral amplitude code (SAC) labelled switching systems for high-speed payload signals with different modulation formats. We consider a payload bit-rate of 40 Gbit/s for an intensity modulation (IM), differential phase shift keying (DPSK), differential quadrature phase shift keying (DQPSK) and 4-channel multi-rate DQPSK payload signals with 2.5, 10, 20 and 80 Gb/s rates for comparison purposes. The label and payload signal performances are assessed by the eye-diagram opening factor (EOF) and bit-error rate (BER) as function of the optical signal-to-noise ratio (OSNR). Our proposed SAC label detection method offers flexible, robust and multi-bit-rate label performance for payload signal with different modulation formats.

Using CAP dimensionality for service and user allocation for optical access networks

The usability of carrierless amplitude and phase (CAP) modulation dimensions for service and user allocation for WDM optical access is experimentally demonstrated in a 2X2D-ODMA configuration.

Digital non-linear equalization for flexible capacity ultradense WDM channels for metro core networking

We experimentally demonstrate that digital non-linear equalization allows for using independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking.

Engineering rules for chromatic dispersion compensation in digital receivers for optical coherent PolMux QPSK links

We consider block overlap chromatic dispersion compensation in optical coherent polarization multiplex quadrature phase shift keying links. We validate engineering rules for block length to compensate different values of chromatic dispersion by simulation and experiment.