H. C. Ji

Full-Duplex Radio-Over-Fiber System Using Phase-Modulated Downlink and Intensity-Modulated Uplink

We propose and demonstrate a full-duplex radio-over-fiber system employing a phase-modulated downlink and an intensity-modulated uplink over a single optical carrier. Each downlink and uplink is encoded with 200-Mb/s 16-quadrature amplitude modulation and a 100-Mb/s quadrature phase-shift keying signal carried in the 6-GHz band, respectively. The demonstration results show that the constraints on modulation index of the downlink signal as well as power budget of uplink signal can be relaxed thanks to the constant intensity of the phase-modulated downlink signal. The results also show the good error vector magnitude performance in both downlink and uplink signals after transmission over a 25-km fiber link. The effect of phase modulation to intensity modulation conversion of the downlink signal is also measured and evaluated for the scalability of the proposed technique.

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.

Cost-effective colorless WDM-PON delivering up/down-stream data and broadcast services on a single wavelength using mutually injected Fabry-Perot laser diodes

We propose and demonstrate for the first time a cost-effective and colorless wavelength-division-multiplexed passive optical network which can provide a full-duplex 155-Mb/s up/downstream data and broadcast signals on a single wavelength using light-injected optical sources and bidirectional transmission in a single fiber. The optical sources for downstream and upstream baseband data are Fabry-Perot laser diode (FPLD) at the central office and a reflective semiconductor optical amplifier (RSOA) at each optical network unit, respectively. The broadband light source (BLS) for the downstream is implemented by using mutually injected FPLDs. The transmission experiment shows that the error-free operation for baseband data and a high-quality broadcast signal with 3-dB CNR margin can be obtained.

A multi-wavelength locker for WDM system

We demonstrate a simple technique to stabilize the wavelengths of WDM lasers using a synchronized etalon filter and a digital signal processing board. The results shows that the proposed technique could maintain the frequency stability of each WDM laser within 200 MHz.

A novel frequency-offset monitoring technique for direct-detection DPSK systems

We propose and demonstrate a novel technique to monitor the frequency offset between the optical signal and delay interferometer in direct-detection DPSK systems. The monitoring range and accuracy of the proposed technique were measured to be /spl plusmn/2 GHz and /spl sim/1 MHz, respectively.

Evaluation on system outage probability due to temperature variation and statistically distributed chromatic dispersion of optical fiber

This paper discusses the evaluation of the system outage probability caused by the temperature variation and statistically distributed chromatic dispersion of optical fiber in a high-speed (>40 Gb/s) optical network. This was to identify when the tunable dispersion compensator should be used at every channel.

Effect of PDL-induced coherent crosstalk on polarization-division-multiplexed direct-detection systems.

We analyze the effect of polarization-dependent loss (PDL) on the performance of the polarization-division-multiplexed (PDM) signals in direct-detection systems. We present the theoretical analysis of the sensitivity penalty caused by PDL-induced coherent crosstalk and compare the results with experimental data obtained by using a simple variable PDL emulator based on a LiNbO3 Mach-Zehnder modulator. Also presented is the performance degradation caused by the polarization misalignment between the received signals and the polarization beam splitter at the receiver in the presence of PDL.

Performance of an OSNR monitor based on the polarization-nullingtechnique

Feature Issue on Optical Performance Monitoring (OPM). We report on the performance of an optical signal-to-noise ratio (OSNR) monitor with the polarization-nulling technique. The results show that this monitor was robust to polarization-mode dispersion and in-band cross talk. For a demonstration, we monitored the OSNR of the optical signal transmitted through a 2×60 km long aerial fiber link for one week and confirmed that the OSNR could be measured with accuracy better than ±0.3 dB (when the OSNR is lower than 26 dB).

Cost-effective WDM-PON Delivering Up/Downstream Data and Broadcast Services on a Single Wavelength Using Mutually Injected FPLDs

We propose and demonstrate a cost-effective wavelength-division-multiplexed passive optical network which can provide 155-Mb/s up/downstream data and broadcast signals on a single wavelength using bidirectional transmission and mutually injected Fabry-Perot laser diodes.

System outage probability due to dispersion variation caused by seasonal and regional temperature variations

We evaluated the system outage probability of high-speed optical network caused by the variation of chromatic dispersion arising from the seasonal and regional temperature variations.