K.H. Han

Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels.

Bidirectional WDM PON using light-emitting diodes spectrum-sliced with cyclic arrayed-waveguide grating

We proposed and demonstrated a bidirectional wavelength-division-multiplexing passive optical network by using spectrum-sliced light-emitting diodes (LEDs) with cyclic arrayed-waveguide gratings (AWGs). When the spectrum-slicing technique is used, it is often difficult to secure an adequate amount of system margin due to the large slicing loss and low output power of LED. To overcome this problem, we reduced the slicing loss by using all the peaks of the spectrum-sliced light (separated by the free-spectral range of AWG) and improved the receiver sensitivity by using the forward-error correction technique. The excessive dispersion penalty (caused by using multiple peaks) was suppressed by using a simple dispersion precompensation circuit.

Survivable network architectures for WDM PON

We propose and demonstrate a simple self-protecting architecture for WDM PON. The protection time was less than 10 ms, and the power penalty caused by the protection process was negligible.

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.

Fault localization in WDM passive optical network by reusing downstream light sources

We propose and demonstrate a simple and cost-effective technique to detect and localize the fiber failures in wavelength-division-multiplexed (WDM) passive optical networks. 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.

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.

Multi-purpose fiber-optic access network (MFAN)

Summary form only given. We have proposed and demonstrated two types of multi-purpose fiber-optic access networks (MFANs) which can be used to support various wired and wireless services using the same fiber infrastructure, including digital baseband, analog CATV, CDMA personal communication service (PCS), wireless local loop (WLL), and local multi-point communication service (LMCS) services. These networks were implemented by using only three wavelengths separated by more than 20 nm. Thus, there was no need to use any complicated wavelength-stabilization circuitry. The crosstalk, caused by either fiber nonlinearities or imperfect demultiplexers, was measured to be negligible. The passive and active MFAN could accommodate 9 ONU/RBSs and 64 ONU/RBSs, respectively. If necessary, the passive MFAN could be gracefully upgraded to its active version.We propose and demonstrate a multi-purpose fiber-optic access network (MFAN). This network utilizes the same fiber infrastructure for a variety of services including baseband, CATV, PCS, WLL, and LMCS. The experimental results show that the proposed network could support the independent operation of these services.

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.

Effects of MPI noise on various modulation formats in distributed Raman amplified system

We evaluated the effect of MPI noise on various modulation formats in a distributed Raman amplified system. The results show that RZ-DPSK is the most tolerant modulation format to MPI noise.