Browsing by Author "Willner, Alan E."

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Bit Error Rate Calculation for a Single Sideband OFDM Signal with Direct Detection Optically Pre-amplified Receivers
(2008)
Peng, Wei-Ren
;
Feng, Kai-Ming
;
Chi, Sien
;
Willner, Alan E.
;
光電工程學系
We provide a fast and accurate BER calculation for a SSB-OFDM signal by considering the SNR of each subcarrier separately. The numerical results show that our scheme can accurately evaluate the BER for different QAM formats even under a strong optical filtering. (C) 2008 Optical Society of America
Compensation for I/Q Imbalances and Bias Deviation of the Mach-Zehnder Modulators in Direct-Detected Optical OFDM Systems
(2009-01-01)
Peng, Wei-Ren
;
Zhang, Bo
;
Wu, Xiaoxia
;
Feng, Kai-Ming
;
Willner, Alan E.
We demonstrate an equalization technique to simultaneously compensate for the fiber chromatic dispersion and the distortions induced by the in-phase/quadrature-phase (I/Q) imbalances and bias deviation in the Mach-Zehnder modulators (MZMs). With this technique, the requirement for the monitoring circuits at the transmitter could be relaxed or even eliminated, and thus simplifies the system design and reduces the system cost. The system exhibits a good performance with our proposal over a broad range of imbalances and bias deviation in the MZM. With deliberately introducing I/Q imbalances and bias deviation, we have observed a 2- and 4-dB optical signal-to-noise ratio improvement, for the back-to-back and 800 km of uncompensated standard single-mode fiber transmission, respectively, with our proposed scheme.
Estimation of the Bit Error Rate for Direct-Detected OFDM Signals With Optically Preamplified Receivers
(2009-05-15)
Peng, Wei-Ren
;
Feng, Kai-Ming
;
Willner, Alan E.
;
Chi, Sien
;
光電工程學系
In this paper, we provide a numerical bit error rate (BER) estimation approach for direct-detected orthogonal frequency division multiplexing (OFDM) signals in the presence of optical preamplified receivers. The individual BER of each subcarrier is first computed by considering their electrical signal-to-noise ratio (SNR), and then the ensemble BER is derived simply by taking the average of all the subcarriers' BERs. The calculated BER is verified by the conventional error-counting approach with high precision and is still accurate with higher quadratic-amplitude modulation (QAM) formats, even under the influences of the optical filtering and polarization mode dispersion (PMD) effects. Based on our simulation approach, the required extra power budget for 16- and 64-QAM relative to 4-QAM format are found to be similar to 3.8 and 8.2 dB, respectively, at a BER of 10(-9) Furthermore, we use this approach to compare the receiving sensitivities and PMD tolerances for the previous proposed gapped and interleaved radio-frequency (RF)-tone-assisted OFDM systems. The results show that the gapped OFDM has a better sensitivity while the interleaved OFDM has a more PMD-tolerable capability.
Experimental Demonstration of 1600 km SSMF Transmission of a Generalized Direct Detection Optical Virtual SSB-OFDM System
(2008-01-01)
Peng, Wei-Ren
;
Zhang, Bo
;
Wu, XiaoXia
;
Feng, Kai-Ming
;
Willner, Alan E.
We experimentally demonstrate a generalized VSSB-OFDM format that judiciously determines the frequency gap between an inserted RF tone and the signal. The proposed scheme for 10 Gbps exhibits similar to 3 dB penalty after 1600 km SSMF transmission, and has an 8 dB improvement over the regular VSSB-OFDM.
Experimental demonstration of 340 km SSMF transmission using a virtual single sideband OFDM signal that employs carrier suppressed and iterative detection techniques
(2008-01-01)
Peng, Wei-Ren
;
Wu, Xiaoxia
;
Arbab, Vahid R.
;
Shamee, Bishara
;
Yang, Jeng-Yuan
We propose and demonstrate a virtual SSB-OFDM with direct detection that uses half the electrical bandwidth by employing an RF tone at the edge of the signal. We transmit 10 Gbps data with a 4-QAM over 340 kin of SSMF with no penalty. (C) 2008 Optical Society of America.
Experimental demonstration of a coherently modulated and directly detected optical OFDM system using an RF-tone insertion
(2008-01-01)
Peng, Wei-Ren
;
Wu, Xiaoxia
;
Arbab, Vahid R.
;
Shamee, Bishara
;
Christen, Louis C.
We experimentally demonstrate an RF-tone assisted OFDM transmission. Our system has a 5-dB better sensitivity compared to the conventional baseband SSB-OFDM and exhibits a negligible penalty transmission after 260 km of SSMF. (C) 2008 Optical Society of America.
Sensitivity Bound for Optically-Preamplified Direct-Detected OFDM Systems Using Spectrally Matched Filters
(2009)
Peng, Wei-Ren
;
Feng, Kai-Ming
;
Willner, Alan E.
;
Chi, Sien
;
光電工程學系
We investigate the sensitivity bound, in terms of OSNR, for direct-detected OFDM systems in presence of optically-preamplified receivers, and show that OSNR requirement for DD-OFDM could theoretically reach that of CO-OFDM using the spectrally matched filters. (C) 2009 Optical Society of America
Spectrally Efficient Direct-Detected OFDM Transmission Incorporating a Tunable Frequency Gap and an Iterative Detection Techniques
(2009-12-15)
Peng, Wei-Ren
;
Zhang, Bo
;
Feng, Kai-Ming
;
Wu, Xiaoxia
;
Willner, Alan E.
We analytically and experimentally demonstrate a linearly field-modulated, direct-detected virtual single-side-band orthogonal frequency-division multiplexing (VSSB-OFDM) system that employs a tunable frequency gap and an iterative detection technique. The VSSB-OFDM that uses no frequency gap, which is referred to as the gapless VSSB-OFDM, is proposed as a spectrally efficient format. Compared with the intensity-modulated SSB-OFDM, the gapless VSSB-OFDM saves half the electrical bandwidth (BW), and exhibits better receiving sensitivity and more robust tolerance against fiber chromatic dispersion (CD). Furthermore, by incorporating a tunable frequency gap between the optical carrier and the OFDM data sideband, the calculating burden of the iterative detection is greatly alleviated and the system performance can be flexibly improved within moderate iterations. The width of the optimum frequency gap is found to be similar to 0.35 sideband BW, which is reached by trading the levels of signal-signal beat interference and the residual image beat interference. Such a gapped VSSB-OFDM system requires fewer iterations to extract the desired data from the interfered signal and exhibits greater robustness against the carrier-to-signal-power ratio (CSPR) variation, compared with the gapless VSSB-OFDM. In this paper, the analytical model of the proposed gapped VSSB-OFDM system will be addressed. In addition, we also successfully conduct a gapped VSSB-OFDM signal transmission over 1600 km of uncompensated standard single-mode fiber (SSMF) with only similar to 3 dB optical SNR (OSNR) penalty, and obtain a significant OSNR sensitivity improvement of 8 dB, compared with the gapless VSSB-OFDM, after such a 1600-km fiber link.
Theoretical and Experimental Investigations of Direct-Detected RF-Tone-Assisted Optical OFDM Systems
(2009-05-15)
Peng, Wei-Ren
;
Wu, Xiaoxia
;
Arbab, Vahid R.
;
Feng, Kai-Ming
;
Shamee, Bishara
In this paper, we propose and experimentally demonstrate a radio frequency (RF)-tone-assisted optical orthogonal frequency-division multiplexing (OFDM) transmission. By inserting an RF tone at the edge of the signal band and biasing the Mach-Zehnder modulator (MZM) at the null point, the proposed system has a better sensitivity and chromatic dispersion (CD) tolerance compared to the previous intensity-modulated single-sideband OFDM (SSB-OFDM). We show analytically that the majority of the linear channel impairments, such as the transmitter, CD, optical filtering, and receiver, can be compensated for by a simple zero-forcing equalizer. Besides, the optimum value of the important parameter, carrier-to-signal-power ratio (CSPR), is analytically obtained and supported via the experimental results. We also observe that the relatively worse sensitivity of the previous SSB-OFDM can be attributed to the limited CSPR. We experimentally demonstrate a 10-Gb/s, 8 quadrature-amplitude modulation (QAM) RF-tone-assisted OFDM transmission, and show that our system has a similar to 5-dB better sensitivity compared to the previous intensity-modulated SSB-OFDM and exhibits a negligible transmission penalty after 260-km uncompensated standard single-mode fiber (SSMF).
Ultimate Sensitivity for Optically Preamplified Direct-Detected OFDM Systems Using Spectrally Matched Optical Filters
(2009-12-01)
Peng, Wei-Ren
;
Feng, Kai-Ming
;
Willner, Alan E.
;
光電工程學系
;
Department of Photonics
We investigate the lower sensitivity bound, in terms of optical signal-to-noise ratio (OSNR), for direct-detected orthogonal frequency-division-multiplexing (DD-OFDM) systems in the presence of optically preamplified receivers. Using the spectrally matched optical filter, which is composed of two parallel filters for the carrier and sideband and has a passband matching to the signal spectrum, the ultimate sensitivity of DD-OFDM is found theoretically to approach that of coherent optical OFDM. We also investigate the effects of the filter's orders and bandwidths to the improved OSNR, and found that these effects could be effectively mitigated via the use of an optical amplifier for the carrier.