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Coherent Optical Transmission Systems: Performance and Coding Aspects
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since the invention of fiber-optic systems in the 1970s, user demand has driven innovation forward, and each new generation of products has achieved higher data rates than its predecessor. Today, the most promising approach for further increasing data rates is coherent transmission with multi-level modulation and digital signal processing (DSP). By using multi-level modulation, data rates can be increased without increasing the spectral bandwidth of the signal. Digital signal processing has a highly-predictable design flow, and solutions are likely to become more attractive in the future as technology scales. As multi-level modulation is very susceptible to noise and distortions, these systems typically include forward error correction (FEC), which fits well with the DSP structure.

In this thesis, we focus on two aspects of DSP-based coherent systems. First, we use a unified approach to analyze theoretical performance limits of coherent optical receivers and microwave receivers, in terms of signal-to-noise ratio (SNR) and bit error rate (BER). By using our general framework, we directly compare the performance of ten coherent optical receiver architectures and five microwave receiver architectures. In addition, we put previous publications into context, and identify areas of agreement and disagreement between them.

Second, we consider simple Bose-Chaudhuri-Hocquenghem (BCH) codes for such systems. While most of coding theory is based on the assumption of additive white Gaussian noise (AWGN) channels, fiber-optic systems have other channel impairments in addition to AWGN. For example, there is relatively high phase noise (PN) from the transmitter and local oscillator (LO) lasers. We present a family of straightforward methods for selecting BCH codes for systems with PN. These codes are highly predictable and systematic to construct. They have low-complexity implementations and no error floor. Our methods are based on simple statistical models that can be parameterized from pre-FEC simulations, thus requiring only modest simulation effort. They are suitable for correcting pre-FEC BERs of around 10^−3. We consider differential quadrature phase-shift keying (DQPSK) modulation and higher-order differential quadrature amplitude modulation (DQAM) with star-shaped constellations.

This thesis is an extension of our licentiate thesis, and improves upon the latter in two significant ways. First, the methods for code selection that were previously limited to DQPSK are now generalized to higher-order star-shaped DQAM formats, which can potentially deliver higher data rates. Second, we consider block interleavers which yield practical low-complexity implementations. These complement our earlier analysis of uniform interleavers, which provide general theoretical insight.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xxi, 75 p.
Series
TRITA-ICT, 2015:20
National Category
Communication Systems Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-176637ISBN: 978-91-7595-759-3 (print)OAI: oai:DiVA.org:kth-176637DiVA: diva2:868095
Public defence
2015-12-14, Sal C, KTH-ICT, Electrum 229, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 0379801EU, FP7, Seventh Framework Programme, 324391
Note

QC 20151119

Available from: 2015-11-19 Created: 2015-11-09 Last updated: 2015-11-19Bibliographically approved
List of papers
1. Receiver sensitivity in optical and microwave, heterodyne and homodyne systems
Open this publication in new window or tab >>Receiver sensitivity in optical and microwave, heterodyne and homodyne systems
2014 (English)In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 35, no 3, 221-229 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we analyze the sensitivities of coherent optical receivers and microwave receivers. We derive theoretical limits of signal-to-noise ratio and bit error rate. By applying a generic approach to a broad range of receivers, we can compare their performance directly. Other publications have considered some of these receivers. However, their diverse nature obscures the big picture. Using our results as a unifying platform, previous publications can be compared and discrepancies between them identified.

Keyword
bit error rate (BER), coherent optical receivers, microwave receivers, receiver sensitivity, signal-to-noise ratio (SNR)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-161029 (URN)10.1515/joc-2013-0164 (DOI)2-s2.0-84906959441 (Scopus ID)
Note

QC 20150312

Available from: 2015-03-12 Created: 2015-03-06 Last updated: 2017-12-04Bibliographically approved
2. Dimensioning BCH Codes for Coherent DQPSK Systems With Laser Phase Noise and Cycle Slips
Open this publication in new window or tab >>Dimensioning BCH Codes for Coherent DQPSK Systems With Laser Phase Noise and Cycle Slips
Show others...
2014 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 21, 4048-4052 p.Article in journal (Refereed) Published
Abstract [en]

Forward error correction (FEC) plays a vital role in coherent optical systems employing multi-level modulation. However, much of coding theory assumes that additive white Gaussian noise (AWGN) is dominant, whereas coherent optical systems have significant phase noise (PN) in addition to AWGN. This changes the error statistics and impacts FEC performance. In this paper, we propose a novel semianalytical method for dimensioning binary Bose-Chaudhuri-Hocquenghem (BCH) codes for systems with PN. Our method involves extracting statistics from pre-FEC bit error rate (BER) simulations. We use these statistics to parameterize a bivariate binomial model that describes the distribution of bit errors. In this way, we relate pre-FEC statistics to post-FEC BER and BCHcodes. Our method is applicable to pre-FEC BER around 10(-3) and any post-FEC BER. Using numerical simulations, we evaluate the accuracy of our approach for a target post-FEC BER of 10(-5). Codes dimensioned with our bivariate binomial model meet the target within 0.2-dB signal-to-noise ratio.

Keyword
Bose-Chaudhuri-Hocquenghem (BCH) codes, coherent communications, cycle slips, forward error correction (FEC), phase noise
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-162978 (URN)10.1109/JLT.2014.2345768 (DOI)000350552200013 ()2-s2.0-84907495302 (Scopus ID)
Note

QC 20150331

Available from: 2015-03-31 Created: 2015-03-26 Last updated: 2017-12-04Bibliographically approved
3. Interleavers and BCH Codes for Coherent DQPSK Systems With Laser Phase Noise
Open this publication in new window or tab >>Interleavers and BCH Codes for Coherent DQPSK Systems With Laser Phase Noise
Show others...
2015 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 7, 685-688 p.Article in journal (Refereed) Published
Abstract [en]

The relatively high phase noise of coherent optical systems poses unique challenges for forward error correction (FEC). In this letter, we propose a novel semianalytical method for selecting combinations of interleaver lengths and binary Bose-Chaudhuri-Hocquenghem (BCH) codes that meet a target post-FEC bit error rate (BER). Our method requires only short pre-FEC simulations, based on which we design interleavers and codes analytically. It is applicable to pre-FEC BER similar to 10(-3), and any post-FEC BER. In addition, we show that there is a tradeoff between code overhead and interleaver delay. Finally, for a target of 10(-5), numerical simulations show that interleaver-code combinations selected using our method have post-FEC BER around 2x target. The target BER is achieved with 0.1 dB extra signal-to-noise ratio.

Keyword
Optical fiber communications, error correction codes, block codes, phase noise, communication systems
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-163953 (URN)10.1109/LPT.2014.2385731 (DOI)000350877700001 ()2-s2.0-84924410228 (Scopus ID)
Funder
Swedish Research Council, 0379801EU, FP7, Seventh Framework Programme, 324391
Note

QC 20150506

Available from: 2015-05-06 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
4. Low complexity BCH codes with optimized interleavers for DQPSK systems with laser phase noise
Open this publication in new window or tab >>Low complexity BCH codes with optimized interleavers for DQPSK systems with laser phase noise
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-177345 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-19Bibliographically approved
5. Dimensioning RS codes for mitigation of phase noise induced cycle slips in DQPSK systems
Open this publication in new window or tab >>Dimensioning RS codes for mitigation of phase noise induced cycle slips in DQPSK systems
Show others...
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

We present a semi-analytical method for dimensioning Reed-Solomon codes for coherent DQPSK systems with laser phase noise and cycle slips. We evaluate the accuracy of our method for a 28 Gbaud system using numerical simulations.

Place, publisher, year, edition, pages
Optical Society of America, 2014
Series
Asia Communications and Photonics Conference, ACPC 2014, ISSN 2162-108X
Keyword
Numerical methods, Photonics, Reed-Solomon codes, Cycle slips, Induced cycle, Laser phase noise, RS codes, Semi-analytical methods
National Category
Communication Systems Telecommunications
Identifiers
urn:nbn:se:kth:diva-168206 (URN)2-s2.0-84942366204 (Scopus ID)978-155752852-0 (ISBN)
Conference
Asia Communications and Photonics Conference, ACPC 2014, Shanghai, China, 11 November 2014 through 14 November 2014
Note

QC 20150528

Available from: 2015-05-28 Created: 2015-05-28 Last updated: 2015-11-19Bibliographically approved
6. BCH codes for coherent star DQAM systems with laser phase noise
Open this publication in new window or tab >>BCH codes for coherent star DQAM systems with laser phase noise
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-177346 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-19Bibliographically approved

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