E. S. Son

Enhanced performance of RSOA-based WDM PON by using Manchester coding

Feature Issue on Passive Optical Network Architectures and TechnologiesWe propose and demonstrate that the power budget and scalability of the wavelength-division-multiplexed passive optical network (WDM PON) implemented by using reflective semiconductor optical amplifiers (RSOAs) can be significantly improved by modulating the downstream signals in Manchester format instead of the conventional non-return-to-zero format. As an example, we experimentally show that the maximum transmission distance of the RSOA-based WDM PON can be increased by a factor of 2 by using the Manchester-encoded downstream signals.

Optical performance monitoring techniques based on pilot tones for WDM network applications

Feature Issue on Optical Performance Monitoring (OPM). We report on the pilot-tone-based optical performance monitoring techniques for use in the wavelength-division multiplexing (WDM) network. We first described the operating principle of the pilot-tone-based monitoring technique and estimated its scalability by analyzing potential problems. We then reviewed the techniques proposed for monitoring various optical parameters of WDM signals--such as optical power, wavelength, optical path, and cross talk--using pilot tones. We also presented examples of various network elements using the pilot-tone-based monitoring technique. In addition, we reviewed the pilot-tone-based monitoring techniques used in adaptive compensators for chromatic dispersion and polarization-mode dispersion, and we discussed their limitations and possible solutions. For example, we demonstrated a simple technique for monitoring the chromatic dispersion and polarization-mode dispersion simultaneously, without their affecting each other, by scrambling the state of polarization of the optical signal.

Bidirectional passive optical network for the transmission of WDM channels with digital broadcast video signals

We have demonstrated a bidirectional PON for the transmission of 2.5-Gbps WDM channels and >70 digital broadcast video signals. This network could be implemented cost-effectively using a single strand of fiber for bidirectional transmission, LEDs for upstream channels, and one receiver for the detection of both the video and baseband signals (5622 Mbps). In addition, the capacity of the proposed network could be upgraded easily by changing the RF filter or using an additional WDM filter and a receiver.

Survivable Network Architectures for Wavelength-division-multiplexed Passive Optical Networks

Abstract.We propose and demonstrate simple architectures with self-protection capability for the wavelength-division-multiplexed passive optical network (WDM PON). By utilizing two different wavelength bands for the neighboring WDM PONs, the proposed networks can recover the disrupted signals through the fiber links of the neighboring WDM PON. The protection time was measured to be less than 9xa0ms, and the power penalty caused by the protection process was negligible.

Pump-to-signal crosstalk in Raman amplifier systems using polarization-multiplexed pump lasers

We have analyzed the relative intensity noise (RIN) of the pump lasers transferred to the signal in a Raman amplifier system using polarization-multiplexed pump lasers. The result shows that this RIN transfer could be reduced by 3 dB using the polarization-multiplexed pump lasers instead of single pump laser. In a Raman amplifier system, the pump modulation could be used for line monitoring. We have also analyzed the power penalty caused by the modulated pump laser in such a system.

Experimental study on the effect of codirectional Raman gain on system's performance.

We have experimentally investigated the impact of codirectional Raman gains on the performance of distributed fiber Raman amplified systems. The effects of various noise sources, such as optical signal-to-noise ratio (OSNR) degradation, fiber nonlinearities and surviving channel gain variation in different Raman pumping schemes, were evaluated as a function of input power into a fiber span. For measurements, distributed Raman gain was generated by pumping the fiber span with different combinations of Raman pump power between co- and counterdirections. From the results, we found that a large counterdirectional Raman gain assisted by a small codirectional gain could improve the overall static and dynamic performance of distributed Raman amplified systems.

Effects of downstream modulation formats on the performance of RSOA-based WDM PON

We evaluate the effects of the downstream modulation formats (such as NRZ, inverse RZ, and Manchester) on the performance of the WDM PON implemented by using the reflective semiconductor optical amplifiers (RSOAs). The results show that, when we modulate the downstream signals in Manchester format, the performance of the upstream signal becomes insensitive to the operating condition of the RSOA.

Temperature-independent fiber-based optical phase conjugation

We have investigated the effect of temperature variation on the performance of fiber-based optical phase conjugation (OPC) module. The results show that the bandwidth of the fiber-based OPC module could be reduced significantly by temperature variation. However, it would be difficult to control the temperature of bulky fiber spool precisely. To solve this problem, we have proposed and demonstrated a simple method to compensate the bandwidth reduction (caused by temperature variation) by adjusting the pump power. Using this method, we could maintain the 1-dB bandwidth of fiber-based OPC module within 5% even when the ambient temperature was varied as much as plusmn15 degC

Design method for bidirectionally pumped distributed Raman amplifier

We develop an efficient design method for the bi-directionally pumped distributed Raman amplifier (DRA). Using this method, we have designed a bi-directionally pumped DRA having a small gain ripple (< 1.1 dB) over the bandwidth of 90 nm.

Fault localization in WDM PON by reusing downstream light sources

We propose and demonstrate a simple and cost-effective technique to detect and localize the fiber failures in WDM PON. By reusing the downstream lasers as WDM light sources for the optical time-domain reflectometry, the proposed technique can localize the failures in both feeder and drop fibers without using the expensive tunable laser.