Phase Modulation Formats Research Articles

Binary CPMs With Improved Spectral Efficiency

We design new continuous phase modulation (CPM) formats which are based on the combination of a proper precoder with binary input and a ternary CPM. The proposed precoder constrains the signal phase evolution in order to increase the minimum Euclidean distance, and to limit the bandwidth expansion due to the use of a ternary CPM. The resulting schemes are highly spectrally efficient and outperform classical binary and quaternary formats in terms of coded and uncoded performance.

A Multi-CAP Visible-Light Communications System With 4.85-b/s/Hz Spectral Efficiency

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into $\boldsymbol{m}$ subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and $\boldsymbol{m}$ , where $\boldsymbol{m}=\{10,8,6,4,2,1\}$ subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of $\boldsymbol{m}$ , respectively.

Performance of Phase Modulation in WDM-PON Transmission System

AbstractThe modulation and demodulation methods of the optical Differential Quadrature Phase Shift Keying (DQPSK), Optical Differential Phase Shift Keying (DPSK) and the different modulation formats including nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero (CS-RZ) are introduced, studying the ability of anti-dispersion for different optical signals in the 40 Gb/s high speed transmission system. The system is simulated in optical fiber by way of dispersion compensation. And then analyzed the compensation effect of the different dispersion compensation method for different phase modulation formats. It is shown that the ability of anti-dispersion and anti-PMD is better in the CS-RZ-DQPSK modulation format, and this format has the smallest eye-opening penalty (EOP) with a wider range of power into the optical fiber.

8PSK Signals with 50% RZ Clock for Optical Access System Applications Using Phase Equalization Technique in MSPE

A multi-symbol phase modulation format, the 8 phase shift keying (8PSK) with 50% return-to-zero (RZ) clock, is proposed and demonstrated in this scheme for 30-Gb/s optical access downlink transmission applications using phase equalization technique in MSPE. RZ-8PSK optical signals are generated by cascading three phase modulators and a dual-arm Mach-Zehnder modulator. Superimposed 50% RZ clock is extracted and recovered for achieving access restoration. The result show the reception performance of 50% RZ-8PSK signals with phase equalization after transmission over SMF-28 is good.

Investigation of Stimulated Brillouin Scattering Effect on Different Modulation Formats

In this study, the impact of Stimulated Brillouin Scattering (SBS) and effective core area and the Brillouin gain coefficient on On-Off Key (OOK) and phase modulation formats is investigated. In comparison with OOK formats, Return to Zero-Differential Phase Shift Keying (RZ-DPSK) revealed more robustness against the SBS effect with regards to jitter. The generated jitter due to power increment from 0 to 6 dBm was measured. The results show 0.1232, 0.1054, 0.0683 and 0.0544 bit period jitter for NRZ-OOK, RZ-OOK 0.5, NRZ-DPSK and RZ DPSK respectively. Furthermore, it is shown that SBS effect changes the behavior of system with regards to bit rate variation. It is shown that lower bit rate, does not guarantee higher performance. For instance, while the log BER at 2 Gb/sec is -11 for RZ-OOK 0.5, -9 for CSRZ,-10 for NRZ-DPSK and -16 for RZ-DPSK, at 8 Gb/sec they hit a peak with -16, -20, -21 and -36, respectively.

Benefits and Limits of Modulation Formats for Optical Communications

This paper is focused on benefits and lim- its of intensity and phase modulation formats used in optical communications. The simulation results are ob- tained using OptSim software environment, employing Time Domain Split Step method. Non-Return to Zero, Return to Zero, Chirped Return to Zero and Carrier- Suppressed Return to Zero formats are compared in terms of Bit Error Rate and spectral eciency to find the limits for selected transmission network topologies. It is shown that phase modulation formats oer many advantages compared to intensity formats. Dierential Phase-Shift Keying and mainly Dierential Quadrature Phase-Shift Keying improve the Bit Error Rate and transmission reach, among others. A promising solu- tion is the application of Polarization Division Multi- plexing Quadrature Phase-Shift Keying, which primar- ily benefits in spectral eciency, estimated reach, opti- cal signal to noise ratio and chromatic dispersion tol- erances.

Integrated Wireless and Wired Signal in the Hybrid Access System

To meet the demands of different high bandwidth services, we demonstrated a hybrid access network simultaneously transmitting wired and wireless signals. In the downstream, wireless signals are modulated and transmitted in phase modulation format at the optical carrier and wired signals are re-modulated in intensity modulation format, different de-modulation schemes are used at optical network unit (ONU) side; In the upstream, carrier reuse technology are adopted to re-modulate and transmit uplink signals to the optical line terminal (OLT). Simulation results show user ends could get acceptable performance of the wirless and wired signals.

Power distribution analysis for multiple modulation formats in an all-optical sampling wavelength division multiplexing system

An optimal power distribution analysis for an all-optical sampling orthagonal frequency division multiplexing (OFDM) scheme with multiple modulation formats including differential phase shift keyed (DPSK), differential quadrature phase shift keyed (DQPSK), and non-return-to-zero (NRZ) is proposed. The noise tolerances of different modulation formats are analyzed, and the optimal input power ratio between phase and intensity modulation formats for the best overall receiving performance is investigated under unchanged total input power. Moreover, this scheme can seamlessly coexist with the traditional WDM channel.

Improved all optical chromatic dispersion monitoring method for WDM systems

In this paper we propose an improved all optical chromatic dispersion (CD) monitoring method applicable to wavelength division multiplexing (WDM) systems with intensity or phase modulation format. This method can operate over a much larger bandwidth and CD monitoring range and is insensitive to optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD). These improvements are achieved by utilizing a wavelength tunable laser as the probe to maintain the appropriate phase-matching condition and a loop-back controlled tunable CD compensator to discriminate CD distortions from PMD and OSNR influences. Numerical simulations show that by this method the operational bandwidth and CD monitoring range can be expanded to cover C+L bands and ±1600ps/nm, respectively, for different modulation formats and the sensitivity is higher than the other methods proposed before.

Novel Demodulation Method for Fiber-Optic Interferometers Based on $\pi/2$ Phase Modulation

This letter proposes a novel demodulation method for fiber-optic interferometer sensors. A fast square wave is added to the reference arm of the interferometer sensor in the form of phase modulation. Starting from this, we successfully developed a simple demodulation method that can greatly improve the conversion efficiency and overcome the unbalanced influences. Our experiment results show that a very small phase shift of about 6.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> rad can be detected, which proves high signal-to-noise ratio demodulated signal and low distortion in our demodulation method. The linearity between demodulated signal and test signal is shown to be over 99%.

Direct modelling of error statistics for data transmission through a high data rate communication line using a four-level phase modulation format

This paper presents mathematical modelling results for information transmission by optical pulses through a fibre-optic communication line at a rate of 80 Gbit s-1 per WDM channel usinga four-level phase modulation format. We examine the influence of nonlinear effects on the profile of optical pulses propagating along the fibre. Using direct optical signal detection, we analyse error statistics and demonstrate an uneven error distribution over various symbol combinations.

Optimization of regenerator based on semiconductor optical amplifier for degraded differential phase shift keying signal

Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.

Statistics of errors in fibre communication lines with a phase-modulation format and optical phase conjugation

Analytical formulas are derived to approximate the probability density functions of 'zero' and 'one' bits in a linear communication channel with a binary format of optical signal phase modulation. Direct numerical simulation of the propagation of optical pulses in a communication line with optical phase conjugation is performed. The results of the numerical simulation are in good agreement with the analytical approximation.

Comparative analysis of high-speed fiber-optic lines using amplitude- and phase-modulated signals

This paper presents the results of a comparative analysis of high-speed fiber-optic communication lines based on phase and amplitude modulation formats.

Effective homodyne optical phase locking to PSK signal by means of 8b10b line coding

We demonstrate a novel technique that allows effective homodyne optical phase locking to a phase shift keying (PSK) signal with a residual carrier. We exploit 8b10b coding of the signal in order to reduce its low frequency spectral content, suppressing the data-to-phase crosstalk effect. In a transmission experiment on a 10 Gb/s binary PSK signal (8 Gb/s before coding), we achieved transmission over 215 km of dispersion-compensated, installed single-mode fibre, with no penalty compared to back-to-back at a bit error ratio of 10(-3). The proposed solution is applicable to other modulation formats, including multi-level amplitude and/or phase modulation formats.

Investigation of Different Modulation Formats Simultaneous Transmission in WDM Systems

For a long time, intensity modulation (IM) format has been the dominant in wavelength division multiplexing (WDM) transmission systems. The major reasons for using were a relatively simple realization of optical transmitter and receiver compared with phase modulation (PSK) format. However, IM format has been less resistive to fiber nonlinearities. In recent years, as fiber optical communication is advancing to mixed signals broadcasting IM and PSK formats simultaneous transmission must be investigated.

Study of the Gordon&amp;#x2013;Mollenauer Effect and of the Optical-Phase-Conjugation Compensation Method in Phase-Modulated Optical Communication Systems

Optical phase-modulated systems are promising candidates for the development of ultrahigh-bit-rate transmission links, thanks to their high spectral efficiency and increased tolerance to fiber-optic nonlinearities. However, their implementation was considerably slowed down by theoretical studies, suggesting that the transmission performance can be severely hindered by nonlinear phase noise (the so-called Gordon-Mollenauer effect). The simulations presented here show that, in realistic systems (including nonlinearity, dispersion, and attenuation), Gordon-Mollenauer noise does not represent the main source of signal distortions. We demonstrate that all nonlinear impairments can be efficiently compensated by optical phase conjugation, independent of system characteristics. The combination of optical-phase-conjugation with phase-modulation formats could enable ultrahigh-transmission-capacity and easy embedded-link upgrading.

Analysis of smooth phase modulation formats compared with conventional QPSK and BPSK using coherent detection

Novel optical offset quadrature phase shift keying (OQPSK) and improved minimum-shift keying (MSK) modulation schemes to smooth optical phase hopping for high speed fiber optics transmission are proposed. Simulations have been done among the MSK, OQPSK, quadrature phase shift keying (QPSK), and binary phase-shift keying (BPSK) modulation formats at 40 Gb/s over 100-km transmission link using coherent detection. Simulation results present good performances to elevate chromatic dispersion tolerance and reduce the influence of nonlinear effects by adopting the smooth phase modulation formats. Inter-symbol interference decreases for the fast side-lobe property and tight spectrum as a result of avoding the ? phase shift and reducing envelop fluctuation.

Nonlinear signal–noise interactions in dispersion-managed links with various modulation formats

Purpose of this paper is to highlight the principles of the nonlinear signal–noise interaction (NSNI) in dispersion-managed long-haul optical links and provide a quantitative understanding of the system parameters for which NSNI sets the nonlinear performance of the most popular intensity and phase modulation formats, namely on–off keying, differential binary and quadrature phase-shift keying and coherent quadrature phase-shift keying.

Maximum-Likelihood Sequence Estimation for Optical Phase-Shift Keyed Modulation Formats

Electronic chromatic dispersion compensation employing maximum-likelihood sequence estimation (MLSE) has recently been the topic of extensive research and a range of commercial products. It is well known that MLSE provides a considerable benefit for amplitude modulated modulation formats such as on-off keying (OOK) and optical duobinary. However, when applied to optical phase modulation formats, such as differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK), it has been shown that the benefit is only marginal. This paper investigates joint-decision MLSE (JD-MLSE) detection applied to 10.7-Gb/s DPSK. It demonstrates that a JD-MLSE using the constructive and destructive components preserves the 3-dB optical signal-to-noise ratio (OSNR) advantage of DPSK over OOK in dispersion-limited optical systems. Furthermore, we demonstrate that the use of a shortened MZDI with MLSE for the 10.7-Gb/s DPSK modulation can equalize an accumulated chromatic dispersion of 4000 ps/nm. In addition, we discuss in this paper different MLSE schemes applied to 2 times 10.7-Gb/s DQPSK modulation. It is shown that a joint-symbol MLSE (JS-MLSE) on the balanced outputs of the in-phase and quadrature components gives the best performance.