The relative impact of in-band crosstalk and amplified spontaneous emission (ASE) noise on a system’s performance has been investigated with a differentially phase-shift keying signal. I have first measured an ASE noise-induced penalty without any in-band crosstalk and then estimated the system’s penalty with a simple addition of the measured ASE noise-induced penalty and the calculated in-band crosstalk-induced penalty. Using this approach, the estimated penalty agreed well with a measured system penalty when the Q value was 3 or an optical signal-to-noise ratio (OSNR) of the signal was higher than 30 dB at Q=6. To estimate the system penalty with a low OSNR level at Q=6, an addition of signal-ASE and signal-in-band crosstalk beat noises were added with a weighting factor. Based on this approach, a discrepancy between the estimated and the measured penalties was reduced drastically with an OSNR of 20 dB at Q=6. However, a small discrepancy was still observed even with the weighted addition of two beat noises. Thus, I have confirmed that the effect of in-band crosstalk–in-band crosstalk beat noise should be taken into account for the proper estimation of a system penalty with an OSNR of <30 dB at Q=6.
In amplified wavelength-division-multiplexed (WDM) networks, the performance of a low-frequency (<100 kHz) pilot-tone-based monitoring technique could be deteriorated by the slow dynamic properties of erbium-doped fiber amplifiers (EDFAs). We develop a simple model to describe this effect and estimate the maximum size of WDM network that the pilot-tone-based monitoring technique could support. The result shows that 100-kHz pilot tones could be used for the cost-effective monitoring of metro optical networks (32 channels, 320-km transmission).
We evaluate the performance of wavelength-locked Fabry-Pérot laser diode and spectrum-sliced ASE source for a high-speed
(beyond 1.25 Gb/s) signal transmission in wavelength-division-multiplexed passive optical networks (WDM
PONs). The impacts of relative intensity noise and fiber chromatic dispersion on the system performance are mainly
investigated. In addition, we analyze the maximum reach of our proposed long-reach WDM PON architecture which
utilize the distributed Raman amplification and pump recycling technique.
We have experimentally investigated a stably tunable multiwavelength erbium-doped fiber ring laser based on phase modulation of a semiconductor optical amplifier with lasing wavelength and spacing tunability at room temperature. Stable multiwavelength operation is obtained by direct modulation of the bias current in the amplifier. We demonstrate such a laser incorporating a tunable Lyot-Sagnac filter with two segments of polarization-maintaining fibers with wavelength-spacing and lasing wavelength tunability. We successfully achieved 1.0-nm-spacing eight-channel and 0.8-nm-spacing ten-channel lasing wavelengths at room temperature. The lasing wavelength of the laser can be also controlled by a polarization controller.
We propose a novel method of tunable compensation for dispersion and dispersion slope based on a uniform fiber Bragg gratings (FBGs). A specially designed mechanical rotator and a metal beam with a thickness gradient can induce a nonlinear strain gradient along the length of the gratings so as to control the dispersion of the gratings and their dispersion slope as well. By way of changing rotation angle, the dispersion value was controlled from -894.6ps/nm to -365.2ps/nm while the dispersion slope from 1049.2ps/nm2 to 134.8 ps/nm2. The centre wavelength was measured to shift by less than 0.07nm. In simulated 80Gb/s NRZ transmission system, we showed to compensate dispersion and dispersion slope with system power penalty of about 2.5 dB by using the proposed method.
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