Phase-induced Intensity Noise Research Articles

A divided spectrum balanced detection technique for intensity noise reduction in SAC OCDMA systems

In this paper we propose a simple divided spectrum balanced detection (DSBD) for spectral amplitude coding (SAC) optical code division multiple access (OCDMA) systems. SAC OCDMA systems are limited by phase induced intensity noise (PIIN), which is a signal dependent source of noise. Our proposed technique reduces the PIIN by dividing the spectrum of the signal into two or more, and detecting each spectrum by a different photodiode. The DSBD scheme reduces the detected optical power at photodetection, thus resulting in a higher mitigation of the PIIN. Theoretical results show that DSBD demonstrate noticeable improvement over traditional balanced detection technique, for example an up to 33% increase in the number of active users can be achieved, and at least 1×10−3b/sHz increase in the spectral efficiency is obtained. However, the SDBD is more complex and append more constrains on system components.

Performance Analysis of SAC-OCDMA Systems Adopting Overlapping PPM Schemes

A fertile technique, for increasing single-user throughput while keeping a constraint on the light pulsewidth, is proposed for spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) systems. In this technique, two-level <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary overlapping pulse-position modulation ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -OPPM) scheme is adopted and each user is assigned two orthogonal code sequences to represent these two levels. The code sequences are selected from a minimum cross-correlation code set. The bit error rate (BER) of the proposed system is derived, taking into account the effects of phase-induced intensity noise, shot noise, and thermal noise in addition to the multiple-access interference. The BER performance of this system is compared to other systems adopting <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -PPM and OOK schemes under same pulsewidth constraints. Our results reveal that, while keeping the BER well below a prescribed threshold, the proposed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -OPPM SAC-OCDMA system achieves higher transmission rate as compared to both <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -PPM and OOK SAC-OCDMA systems under same constraints. Specifically the transmission rate of a single user of the proposed system can be increased by about 34.44% as compared to traditional systems.

Diagonal Eigenvalue Unity (DEU) code for spectral amplitude coding-optical code division multiple access

Code with ideal in-phase cross correlation (CC) and practical code length to support high number of users are required in spectral amplitude coding-optical code division multiple access (SAC-OCDMA) systems. SAC systems are getting more attractive in the field of OCDMA because of its ability to eliminate the influence of multiple access interference (MAI) and also suppress the effect of phase induced intensity noise (PIIN). In this paper, we have proposed new Diagonal Eigenvalue Unity (DEU) code families with ideal in-phase CC based on Jordan block matrix with simple algebraic ways. Four sets of DEU code families based on the code weight W and number of users N for the combination (even, even), (even, odd), (odd, odd) and (odd, even) are constructed. This combination gives DEU code more flexibility in selection of code weight and number of users. These features made this code a compelling candidate for future optical communication systems. Numerical results show that the proposed DEU system outperforms reported codes. In addition, simulation results taken from a commercial optical systems simulator, Virtual Photonic Instrument (VPI™) shown that, using point to multipoint transmission in passive optical network (PON), DEU has better performance and could support long span with high data rate.

Performance evaluation of Fi-Wi network based on SCM–optical code division multiple access architecture

This paper investigates the performance of a spectral amplitude coding (SAC)–OCDMA system design utilizing subcarrier multiplexing techniques for use in the popular fiber-wireless (Fi-Wi) technology. Zero cross correlation code is employed because of its ability to eliminate phase induced intensity noise (PIIN) and the simplicity of using a direct detection technique at the receiving end. The performances are evaluated theoretically to derive the signal-to-noise ratio and results are presented in terms of bit error rates (BER). Results are analyzed to investigate the effect of code weight and variable data rates on the system performance. To validate the results, simulative analysis is also done using Optisys version 6.0. We demonstrated that the ZCC code performed better compared to other code for a BER floor of 10−9 with larger cardinality of subscribers. Results obviously indicate that system performance can be improved with larger code weight. In addition, the choice of lower bit rate is observed to perform better and more suitable for application in this hybrid Fi-Wi network.

Cardinality enhancement of spectral/spatial modified double weight code optical code division multi-access system by PIIN suppression

A new two-dimensional (2-D) optical code division multiple access (OCDMA) scheme to increase the achievable system capacity is proposed. The code exhibits good cross-correlation property time and wavelength shift. Performances are analyzed on code size and correlation properties affecting two important system parameters, bit error rate (BER) as a function of cardinality generated and optical power transmission requirement. The proposed system can effectively suppress phase-induced intensity noise (PIIN) and has multi-access interference (MAI) cancellation property. Results in a good agreement indicate that 2-D modified double weight (MDW) offers 163.7% and 336.2% larger cardinality compare to 2-D perfect difference code (PDC) and 2-D modified quadratic congruence (MQC) code. By increasing spatial code (N) and keeps similar code length system performance can be further optimized. 2-D MDW (M=45, N=18) accommodates 252.2% and 18.3% cardinality increment and low effective transmitted power (Psr) at −17.9dBm, compare to 2-D MDW (M=247, N=3) and (M=84, N=9) at 10−9 BER error floor. The architecture of the spectral/spatial MDW OCDMA system with property of MAI cancellation is presented.

A Study of Modified Prime Codes Optical CDMA for Wired-Wireless System

In this study, we propose optical code-division multiple-access (OCDMA) network for the radio-over-fiber (RoF) transmissions. The network encoder/decoders (codecs) are structured on the basis of arrayed-waveguide-grating (AWG) routers coded with modified prime codes (MPCs). Performances are numerically evaluated with the effect of phase-induced-intensity-noise (PIIN). It showed that the new code families with lower cross correlation can suppress the intensity noise and cancel out the multiple-access interference (MAI) in balanced detection process effectively and hence improve the system performance. By the proposed MPC-coded OCDMA ROF network codecs, each network requires only two AWG routers to accomplish spectral coding of radio base station (RBS) and decoding of control station (CS), thus, resulting in a simpler and lower cost system. It is possible to accomplish interference- and crosstalk-free optical CDMA system for RoF transmissions.

A new code design for spectral amplitude coding optical CDMA systems using fiber bragg-grating

In this paper, we present the performance of a new code called Dynamic Cyclic Shift (DCS) code for Spectral Amplitude Coding (SAC) optical Code Division Multiple Access (CDMA) networks, using Fiber Bragg-Grating (FBG). FBG consists of a fiber segment whose index of reflection varies periodically along its length. One of the important properties of the DCS code is that the cross-correlation ≤1 between the code words, which means that the Phase Induced Intensity Noise (PIIN) is reduced. We find that the performance of the DCS code is better than Random Diagonal (RD) and Modified Frequency Hopping (MFH). It is observed through simulation and theoretical results that the bit-error rate (BER) of the DCS code significantly better than other codes. Proof –of-principle simulations of encoding with six channels, and 10 Gb/s data transmission is successfully demonstrated together with FBG Encoder/Decoder scheme.

Alleviation Noise Effect Using Flexible Cross Correlation Code in Spectral Amplitude Coding Optical Code Division Multiple Access Systems

A new code for Spectral Amplitude Coding - Optical Code Division Multiple Access (SAC-OCDMA) is proposed and is called Flexible Cross-correlation (FCC) code. The FCC code possesses various advantages; including easy code construction using Tridiagonal matrix compared to other SAC-OCDMA codes such as MDW, MQC and MFH, shorter code length and the important properties of this code is the flexible cross-correlation. Our results reveal that FCC code can effectively alleviated Phase Induced Intensity Noise (PIIN) and allows large cardinality and improve the bit error rate performance.

Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4×10−28 for SPD technique is much better compared to 9.3×10−6 and 9.6×10−3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations.

Performance Enhancement of Optical CDMA by Differential-Phase Method for Radio-over-Fiber Transmissions

The study proposes the differential-phase optical code-division multiple-access (OCDMA) network for radio-over-fiber (RoF) transmissions, and the characteristics are numerically analyzed. The network coder/decoders (codecs) are structured on the basis of arrayed-waveguide-grating (AWG) routers with complementary Walsh-Hadamard (CWH) signature codes. In the proposed system, the network requires only two AWG routers to accomplish spectral encoding of radio base station (RBS) and decoding of control station for the complementary keying, thus resulting in a simpler and low cost system. Performance analyses are evaluated with the dominant noise of phase-induced intensity noise (PIIN) in spectral code OCDMA network. By the proposed AWG-based OCDMA with the differential-phase scheme, it is possible to establish interference-free and low crosstalk beat noise RoF systems.

SOA/SPD-based incoherent SAC-OCDMA system at 9&lt;I&gt;×&lt;/I&gt;5Gbps

To boost the performance of spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems, the need for an effective solution to diminish phase-induced intensity noise (PIIN) is becoming progressively more crucial. In this letter, two PIIN suppression approaches: semiconductor optical amplifier (SOA)-based noise cleaning, and single photodiode detection (SPD) are employed. The performance of the hybrid SOA/SPD scheme is validated through simulation experiments. Our results show that SOA/SPD scheme remarkably improves the performance and increases the throughput of SAC-OCDMA system.

Efficient Use of PPM in Spectral-Amplitude-Coding Optical CDMA Systems

A prominent technique, for reducing the effect of phase-induced intensity noise (PIIN) in spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) systems, is proposed. In this technique, each user is assigned two orthogonal code sequences, selected from a minimum cross-correlation code set. In addition, two-level M -ary pulse-position modulation (MPPM) scheme is adopted, where each level corresponds to a code sequence. This technique decreases the effect of PIIN and allows transmission at high data rates. The bit error rate (BER) of the proposed system is derived, taking into account the effects of PIIN, shot noise, and thermal noise. Two performance measures of this system, namely the BER and maximum achievable number of users, are compared to that of traditional systems adopting complementary and non-complementary keying. Our results reveal that the proposed technique allows each user to transmit at high data rates, compared to traditional techniques, while keeping the BER well below a prescribed threshold. Finally, our results are extended to higher levels of MPPM schemes with multicode modulation.

Two-Dimensional Spectral/Spatial Fiber-Optic CDMA PON with EMS/EPD Codes

This paper proposes an extended M-sequence/extended perfect difference (EMS/EPD) code family which can be applied to a two-dimensional (2-D) spectral/spatial (SS) fiber-optic code division multiple access (FO-CDMA) passive optical network (PON) with interference elimination. In addition, the proposed code family can effectively suppress the effect of phase-induced intensity noise (PIIN) and has a flexible size and the cyclic property. By using an extending technique, the number of fibers is substantially reduced between the remote node (RN) and the optical network units (ONUs). Furthermore, we design a compact optical line terminal (OLT) using the arrayed waveguide grating (AWG) router at the central office (CO) and simple ONUs using the thin-film filters (TFFs) at end users. Based on the mathematical analysis and numerical results, the 2D SS EMS/EPD code family is suitable for high-rate transmission with very good performance.

A non-coherent SAC-OCDMA system using extended quadratic congruence codes for two-code keying scheme in passive optical networks

In this paper, we propose a family of extended quadratic congruence codes for two-code keying (TCK) with the corresponding encoding/decoding architecture for passive optical networks (PONs) in spectral amplitude coding optical code division multiple access (OCDMA) systems. The proposed system can simultaneously eliminate multi-user interference (MUI) and further suppress phase-induced intensity noise (PIIN). We reduce the complexity of the encoding/decoding architecture of the optical line terminal reduced by exploiting arrayed waveguide gratings (AWGs) and the properties of the extended quadratic congruence codes (EQC codes). Moreover, we also design a deployment method to increase the number of simultaneous users. Our numerical results demonstrate that the proposed system outperforms the improved quadratic congruence codes (improved QC codes).

Tunable coherence-free microwave photonic bandpass filter based on double cross gain modulation technique

A tunable, coherence-free, high-resolution microwave photonic bandpass filter, which is compatible to be inserted in a conventional fiber optic link, is presented. It is based on using two cross gain modulation based wavelength converters in a recursive loop. The double cross gain modulation technique solves the semiconductor optical amplifier facet reflection problem in the conventional recursive structure; hence the new microwave photonic signal processor has no coherent interference and no phase-induced intensity noise. It allows arbitrary narrow-linewidth telecommunication-type lasers to be used while enabling stable filter operation to be realized. The filter passband frequency can be tuned by using a wavelength tunable laser and a wavelength dependent time delay component. Experimental results demonstrate robust high-resolution bandpass filter operation with narrow-linewidth sources, no phase-induced intensity noise and a high signal-to-noise ratio performance. Tunable coherence-free operation of the high-resolution bandpass filter is also demonstrated.

Comments on “An Enhanced Detection Technique for Spectral Amplitude Coding Optical CDMA Systems”

It has been shown in the above letter that the use of multiphotodiode balanced detection (MPBD), in spectral-amplitude coding optical code-division multiple-access systems, reduces the effect of phase-induced intensity noise (PIIN) at a cost of added complexity. In this letter, we show that this claim is not true, and the MPBD scheme retains the effects of PIIN as the conventional balanced detector does.

Mitigation of multiple access interference using two-dimensional modified double weight codes for optical code division multiple access systems

We proposed newly two-dimensional (2- D ) spectral amplitude coding optical code division multiple access (OCDMA) scheme using modified double weight (MDW) code capable of suppressing phase-induced intensity noise (PIIN). The architecture of the spectral/spatial MDW OCDMA system with the property of multi-access interference cancellation is presented. The proposed code exhibits good cross-correlation property. At the optimized data transmission rate of 0.745 Gbps, 2-D MDW, M = 63, N = 3, reaches maximum cardinality of 200% increases compared to 2- D perfect difference code, M = 57, N = 3. The performance is severely deteriorated if the data rate further increases above 0.745 Gbps. The proposed code meets the optical transmission requirements at 10−9 bit error rate error floor, with lowest effective transmitted power ( P sr), −17.5 dBm, in comparison to the others through minimizing interference noise that result in PIIN suppression. The proposed system reaches optimum requirements performance in terms of cardinality, data transmission rate, and low effective transmitted power.

All-optical coherence-free microwave filter based on remodulation scheme utilizing different intensity modulators

A simple all-optical coherence-free microwave notch filter is proposed and experimentally demonstrated. The filter is based on remodulation scheme using a narrow-linewidth laser, an intensity electro-optic modulator, and a Sagnac fiber loop reflector to eliminate the coherent limitation and phase-induced intensity noise. Both Mach-Zehnder modulator and electroabsorption modulator are used in the microwave photonic filtering system, and different frequency responses are observed, respectively, in the experiment. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:993–995, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26687

New approach for evaluation of the performance of spectral amplitude coding-optical code division multiple access system on high-speed data rate

In this study, the authors proposed a new approach to evaluate the system performance of spectral amplitude codingoptical code division multiple access (SAC-OCDMA) systems. The system performance is evaluated based on a new code called the dynamic cyclic shift (DCS) code. The bit-error-rate (BER) performance of the DCS code on high-speed SAC-OCDMA systems has been analysed and reported in this study. The most remarkable trait of the newly developed DCS code is that the cross-correlation is variable between 1 and 0, and the phase induced intensity noise is low. In order to evaluate the performance of the DCS code in high-speed SAC-OCDMA system, the mathematical analysis has been extensively derived along with the simulation analysis at 10 Gbit/s, which is carried out by using 'Optisys TM ver.9 simulation software from Optiwave'. The results obtained for the DCS code were compared with those obtained from different coding schemes [e.g. random diagonal code and modified quadratic congruence code] for the same number of interfering users. It has been observed that the DCS code of BER equal to 10 -11 can support high data rate (5 Gbit/s) at 60 km transmission link.

Improving spectral efficiency of SAC-OCDMA systems by SPD scheme

This letter presents a single photodiode detection (SPD) as an effective technique for eradicating both multiple-access interference (MAI) and phase-induced intensity noise (PIIN) in spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. Mathematical analysis and simulation experiments are used to investigate the spectral efficiency (SE) of SAC-OCDMA systems utilizing different detection techniques. Results show that the SPD technique significantly enhances the SE compared to AND as well as modified-AND subtraction detections.