Experimental comparison of 40 Gbit/s RZ and NRZ transmission over standard singlemode fibre

Ellis³

et al. 2008

Opt. Express

Abstract:The optimization of a wavelength tunable RZ transmitter, consisting of an electro-absorption modulator and a SG DBR tunable laser, is carried out using a linear spectrogram based characterization and leads to 1500 km transmission at 42.7 Gb/s independent of the operating wavelength. We demonstrate that, to ensure optimum and consistent transmission performance over a portion of the C-band, the RF drive and bias conditions of the EAM must be varied at each wavelength. The sign and magnitude of the pulse chirp (characterized using the linear spectrographic technique) is therefore tailored to suit the dispersion map of the transmission link. Results achieved show that by optimizing the drive and DC bias applied to the EAM, consistent transmission performance can be achieved over a wide wavelength range. Failure to optimize the EAM drive conditions at each wavelength can lead to serious degradation in system performance.

Section: Introductionmentioning

confidence: 99%

Optimization of a 427 Gb/s wavelength tunable RZ transmitter using a linear spectrogram technique

Maher

Ellis³

et al. 2008

Opt. Express

“…Optical time division multiplexing (OTDM) and hybrid wavelength division multiplexing (WDM)/OTDM are technologies that could be used for greatly increasing the capacity of optical communication systems without increasing the cost (by avoiding high-speed electronics). As optical systems move towards higher data rates and also migrate from non-return to zero (NRZ) to return to zero (RZ) format (due to enhanced performance of RZ systems at 40 Gbit/s and beyond) [2], the impact of chromatic dispersion in transmission fiber becomes more dramatic and the use of dispersion management techniques and/or optical fiber nonlinearities to counteract the dispersive effects, must be precisely regulated [3]. In addition to knowing the dispersion parameter of the transmission fiber, it is essential to know the chirp, pulse width and ER of the optical data signals generated at the transmitter of these high-speed systems.…”

Section: Introductionmentioning

confidence: 99%

Optimized performance map of an EAM for pulse generation and demultiplexing via FROG characterization

Maher

Barry

2007

Optics Communications

Abstract:We demonstrate the complete characterization of a sinusoidally driven electro-absorption modulator (EAM) over a range of RF drive voltages and reverse bias conditions. An accurate performance map for the EAM, to be employed as a pulse generator and demultiplexer in an optical time division multiplexed (OTDM) system, can be realized by employing the Frequency Resolved Optical Gating technique. The generated pulses were characterized for chirp, extinction ratio (ER) and pulse width (< 4 ps). The optimization of the EAM's drive conditions is important to ensure that the generated pulses have the required spectral and temporal characteristics to be used in high-speed systems. The ER and pulse width also influence the demultiplexing performance of an EAM in an OTDM system. This is confirmed by utilizing the EAM as a demultiplexer in an 80 Gb/s OTDM system and measuring the BER as a function of the received optical power for various values of the ER and pulse width. Simulations carried out verified the experimental results achieved.

“…In order to achieve line rates of 40 Gb/s and higher, it may become necessary to use return-to-zero (RZ) coding. RZ (pulse) modulation formats offer a number of advantages over NRZ modulation schemes [2]. First, for high-speed long-haul systems, RZ modulation maintains signal integrity over longer distances as it travels through the network.…”

Section: Introductionmentioning

confidence: 99%

Optimized pulse source for 40-Gb/s systems based on a gain-switched laser diode in conjunction with a nonlinearly chirped grating

Clarke

IEEE Photon. Technol. Lett.

Reid

et al. 2005

Abstract-The authors demonstrate the generation of short optical pulses, which display spectral sidemode suppression ratio, and temporal pedestal suppression ratio, well in excess of 30 dB. The exceptional spectral and temporal characteristics exhibited by these pulses are attained by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a nonlinearly chirped grating. Using this technique, near transform limited 7-ps optical pulses, exhibiting a time bandwidth product of 0.49, are generated.