Browsing by Author "Wu, Xiaoxia"

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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.
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.
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).
Tunable optical wavelength conversion of OFDM signal using a periodically-poled lithium niobate waveguide
(2009-05-25)
Wu, Xiaoxia
;
Peng, Wei-Ren
;
Arbab, Vahid
;
Wang, Jian
;
Willner, Alan
We experimentally demonstrate tunable optical wavelength conversion of a 10-Gb/s radio frequency (RF)-tone assisted orthogonal-frequency-division-multiplexing (OFDM) signal with similar to-5 dB (similar to 30%) efficiency over similar to 30 nm bandwidth using a periodically-poled lithium-niobate (PPLN) waveguide. A penalty of < 3 dB is obtained after wavelength conversion. Quadrature amplitude modulation (QAM) size and subcarrier number are varied to further evaluate the performance of the wavelength converter. (C) 2009 Optical Society of America