Jie Hyun Lee

First Commercial Deployment of a Colorless Gigabit WDM/TDM Hybrid PON System Using Remote Protocol Terminator

Colorless gigabit wavelength-division-multiplexing (WDM)/time-division-multiplexing (TDM) hybrid passive optical network (PON) using a remote protocol terminator is proposed and experimentally demonstrated. The system consists of reflective semiconductor optical amplifier-based WDM-PON and a legacy TDM-PON, combined with a simple and efficient remote node structure in order to provide high-speed fiber-to-the-home service to a large area with a high population density. The demonstrated system can support 512 subscribers with a single feeder fiber. The performance and feasibility of the system were evaluated by transmitting gigabit per second data including the effects of Rayleigh backscattering and 20 km attenuation. The system has been used by Korea Telecom to provide commercial services in Gwangju, Korea, since March 2009, after successfully passing through the benchmark test. This is the first commercial deployment of a WDM/TDM hybrid PON. It can accommodate field-deployed TDM-PON link without any modification and extend the maximum total reach of PON link by the use of remote protocol termination. Number of subscribers and the allocated bandwidth to the subscribers can be designed by simply changing the splitting ratio.

Tunable external cavity laser based on polymer waveguide platform for WDM access network

We developed a wide-range wavelength tunable external cavity lasers based on a polymer waveguide platform for use in wavelength-division-multiplexing (WDM) access networks as a low-cost light source. The lasing wavelength is tuned over 13 nm by thermally changing the reflection spectrum of the polymer waveguide Bragg grating with a heater. With the sidemode suppression ratio higher than 30 dB, it can support 16 WDM channels spaced by 100 GHz. The directly modulated 1.25-Gb/s data streams were successfully transmitted over the single-mode optical fiber link of 20 km.

Optical Transceiver employing an RSOA with Feed-Forward Current Injection

We propose an optical transceiver employing an RSOA of which gain is controlled by feedforward current. With a low injection power below the gain saturation, the improved remodulation is clearly demonstrated at 1.25- Gb/s data rate.

Loop-back WDM-PON with 100 Gb/s capacity using spectrally sliced ASE injected RSOA

We experimentally investigated the 1.25 Gb/s operation of a spectrally sliced amplified spontaneous emission (ASE) injected reflective semiconductor optical amplifier (RSOA) with 50 GHz channel spacing using an injection current adjustment, dispersion management, and the use of an optical receiver with an optimized decision threshold level. We mitigated the relative intensity noise (RIN) degradation caused by post-filtering through the injection current adjustment, and also alleviated the dispersion-induced RIN degradation with the help of the dispersion management method. Finally, the use of an optical receiver with an optimized decision threshold level eliminated error floors, which were attributed to an unequal noise distribution between the mark level and the space level. We also successfully demonstrated a loop-back wavelength division multiplexing-passive optical network (WDM-PON) with a 100 Gb/s (80 × 1.25 Gb/s) capacity using a spectrally sliced ASE injected RSOA by means of the three aforementioned methods. We also analyzed and examined the transmission impairments, such as the dispersion penalty and back-reflection induced penalty, in a 1.25 Gb/s bidirectional WDM-PON based on an RSOA with 50 GHz channel spacing.

Filtering effects in a spectrum-sliced WDM-PON system using a gain-saturated reflected-SOA

We have investigated optical filtering-effects when a spectrally-sliced ASE light is injected to a gain-saturated R-SOA. The resulting distortion in the output optical spectrum from an optical pass-band shape of AWG could significantly affect the transmission quality of the WDM-PON.

Enhancement of power budget in RSOA based loop-back type WDM-PON by using the cascaded RSOAs

In the RSOA based remodulation WDM-PON link, the quality of the upstream performance largely depends on the downstream, such as downstream ER and the received optical power, which directly connected to the link power budget. By cascading RSOAs in the ONU, aforementioned link design constraints were alleviated; the link power budget can be increased by 10 dB when the downstream ER of 5 dB.

Frequency detuning effects in a loop-back WDM-PON employing gain-saturated RSOAs

We report that, in a loop-back wavelength-division-multiplexed passive optical network link with gain-saturated reflective semiconductor optical amplifiers, the upstream performance is strongly affected not only by the gain saturation but also by the selective spectral filtering caused by the frequency difference between the optical downstream signal and the cascaded filters passband. We experimentally investigate these effects and propose to use an additional negatively detuned optical filter at an optical network terminal to improve the upstream transmission performance

Self-wavelength initialization method for the Bragg-grating based tunable light source in WDM passive optical network

We propose a self-wavelength initialization method for the waveguide Bragg-grating based tunable external cavity laser. Reflection characteristics of the Bragg-grating, and the wavelength routing property in the wavelength division multiplexing-passive optical network (WDM-PON) were used in our proposed method. By adding a cost-effective and low- power broadband light source in the central office, the tunable laser can align its output wavelength with the wavelength at the center of the pass band of the WDM multiplexer. This method can be applicable for the Bragg-grating based tunable laser, which is placed either in the central office or in the subscriber region. The operating principle and the feasibility of the proposed method were described by evaluating the transmission performance. By using our initialization method, a tunable laser with a Bragg-grating can be used as a true colorless light source for the WDM-PON.

Improving transmission performance in EIN limited 2.5 Gb/s spectral slicing loop-back WDM-PON based on RSOA employing the dispersion management

We successfully demonstrated EIN-limited 2.5 Gb/s spectral slicing loop-back WDM-PON based on RSOA by using the dispersion management.

Real-time demonstration of QoS guaranteed 25-Gb/s PON prototype with Ethernet-PON MAC/PHY and cost-effective APD receivers for 100-Gb/s access networks.

We demonstrate a real-time 25-Gb/s PON prototype with ethernet-PON MAC/PHY, O-band transmitter, and cost-effective APD receivers. With applying parasitic inductance and capacitance reduction, the frequency response of 25-Gb/s APD ROSA with TO46-pacakge is improved to support high receiver sensitivity around -25 dBm at the BER of 10-3. The 30 dB power budget of 25 Gb/s downstream is achieved at the BER of 10-3. With long-term ethernet packet transmission, 25 Gigabit and 10 Gigabit ethernet traffics are successfully transmitted through the 20-km SMF over 14 hours observation window. Furthermore, QoS and bandwidth re-assignment function of the 25-Gb/s PON prototype are successfully demonstrated with respect to residential, business and mobile backhaul services in ONUs.