Chul Han Kim

Design of bidirectionally pumped fiber amplifiers generating double Rayleigh backscattering

Optimum pumping schemes for bidirectionally pumped distributed fiber amplifiers are evaluated that simultaneously minimize the beat noise between signal and amplified spontaneous emission, as well as between signal and double Rayleigh backscattering. A way of adding a constraint on signal power to describe operation in a strong Kerr fiber nonlinearity regime is included. We show that one can find an optimum Raman net gain, as well as a percentage of forward to total Raman pumping maximizing the signal-to-noise ratio at the end of a transmission line using bidirectionally Raman-pumped transmission fibers.

Single, Depolarized, CW Supercontinuum-Based Wavelength-Division-Multiplexed Passive Optical Network Architecture With C-Band OLT, L-Band ONU, and U-Band Monitoring

We propose and experimentally demonstrate a novel bidirectional wavelength-division-multiplexed passive optical network architecture that fully utilizes the superior optical properties of an incoherent continuous-wave (CW) supercontinuum (SC) source. The proposed architecture, which incorporates low-cost Fabry-Perot laser diodes that have been wavelength locked by spectrum-sliced beams from a depolarized 130-nm-bandwidth CW SC source, is based on a unique wavelength band allocation scheme of the C-band for an optical line terminal (OLT), the L-band for optical network units (ONUs), and the U-band for channel monitoring. A cost-effective network that features a single broadband source at the OLT, and no additional wavelength- band-selective monitoring beam reflector at each ONU can be readily achieved. The experimental demonstration presented in this paper is carried out at a data rate of 622 Mb/s over a 25-km standard single-mode fiber.

WDM-Based Passive Optical Network Upstream Transmission at 1.25 Gb/s Using Fabry–PÉrot Laser Diodes Injected With Spectrum-Sliced, Depolarized, Continuous-Wave Supercontinuum Source

We experimentally demonstrate the use of low-cost Fabry-Perot laser diodes (FP-LDs) injected with spectrum-sliced beams from our proposed, depolarized, high-power, continuous-wave (CW) supercontinuum (SC) for upstream transmission in a wavelength-division-multiplexed (WDM) passive optical network. A ~500-mW CW SC with a ~130-nm bandwidth is obtained from a narrowband, amplified spontaneous emission (ASE) seed of a pumped erbium fiber by nonlinear effects such as modulation instability and stimulated Raman scattering in a highly nonlinear optical fiber. Through measurements of relative intensity noise at various wavelengths, it is shown that our spectrum-sliced SC offers the same performance as the spectrum-sliced erbium ASE. Error-free 25-km upstream transmission for six WDM signals generated from the CW SC-injected FP-LDs, is readily achieved at 1.25 Gb/s

Raman amplification-based WDM-PON architecture with centralized Raman pump-driven, spectrum-sliced erbium ASE and polarization-insensitive EAMs

We propose a novel wavelength division multiplexed (WDM) passive optical network (PON) architecture based on the distributed Raman amplification and pump recycling techniques, which features fully bidirectional transmission, relaxed signal power margin, and active light source-free, colorless subscriber units. The reuse of non-negligible residual Raman pump power as a pump for an erbium fiber-based upstream broadband ASE source allows for fully-centralized control of light sources at optical network units (ONUs), while distributed Raman amplification over a transmission link enables us to obtain lossless low power signal transmission. Furthermore, low-cost and colorless ONUs can be realized by use of the Raman pump-recycled erbium ASE and polarization-insensitive electroabsorption modulators. Error-free upstream transmission over a 50 km fiber link is successfully achieved at a data rate of 622 Mbit/s.

Effects of In-Band Crosstalk in Wavelength-Locked Fabry–PÉrot Laser-Diode-Based WDM PONs

We investigated the impact of in-band crosstalk on the systems performance in wavelength-locked Fabry-Perot laser-diode (FP-LD)-based wavelength-division-multiplexed passive optical networks (WDM PONs). As expected, wavelength-locked FP-LD, which was injected by using an incoherent broadband light source, was more tolerant to in-band crosstalk than distributed-feedback (DFB) laser diode. A 1-dB power penalty in the wavelength-locked FP-LD-based PON system was observed when the crosstalk-to-signal ratio was ~-9 dB. We also compared the measured power penalties with the calculated power penalties. It has been shown that the in-band crosstalk-induced power penalty in wavelength-locked FP-LD-based WDM PON could be estimated properly by taking into account both effects of power addition and signal-crosstalk beat noise.

Effects of intraband crosstalk on incoherent light using SOA-based noise suppression technique

We investigate the effects of intraband crosstalk on the intensity noise suppression of spectrum-sliced incoherent light sources using semiconductor optical amplifiers (SOAs). Both Q-factor and electrical spectrum measurements clearly show that intraband crosstalk deteriorates the SOA-based noise suppression by breaking the correlation between optical frequency components of light.

An Amplified WDM-PON Using Broadband Light Source Seeded Optical Sources and a Novel Bidirectional Reach Extender

We demonstrated the feasibility of an amplified wavelength-division multiplexed passive optical network (WDM-PON) architecture based on broadband light source (BLS) seeded optical sources and a novel bidirectional reach extender. Our bidirectional reach extender could provide an amplification of both downstream and upstream signals as well as a BLS output for the upstream WDM signal generation. An error-free 1.25 Gb/s signal transmission over a 100-km long single-mode fiber was achieved in a bidirectional WDM-PON using BLS seeded reflective semiconductor optical amplifier (RSOA) sources.

Side-mode Suppressed Multiwavelength Fiber Laser and Broadcast Transmission

We demonstrate a side-mode suppressed multi-wavelength fiber laser by use of a semiconductor optical amplifier (SOA) with a coupled ring cavity configuration. Using this light source, we have experimentally investigated transmission performance in WDM-PON.

Analysis of maximum reach in WDM PON architecture based on distributed Raman amplification and pump recycling technique

We analyze the performance of bidirectional WDM PON architecture which utilizes distributed Raman amplification and pump recycling technique. The maximum reach at data rates of 622 Mb/s and 1.25 Gb/s in the proposed WDM PON architecture is calculated by taking into account the effects of power budget, chromatic dispersion of transmission fiber, and Raman amplification-induced noises with a given amount of Raman pump power. From the result, the maximum reach for 622 Mb/s and 1.25 Gb/s signal transmission is calculated to be 65 km and 60 km with a Raman pump power of 700 mW, respectively. We also find that the calculated results agree well with the experimental results which were reported previously.

Performance Evaluation of Bidirectional Optical Amplifiers for Amplified Passive Optical Network Based on Broadband Light Source Seeded Optical Sources

We have evaluated the performances of bidirectional optical amplifiers which were suited for the cost-effective implementation of amplified bidirectional passive optical networks (PONs). First, we measured the maximum gains of two simple bidirectional optical amplifiers implemented without using any optical components for the suppression of reflected signals. From the results, the maximum gains of two simple bidirectional amplifiers with a broadband light source (BLS) seeded optical source were limited to be 27 dB due to the reflection-induced in-band crosstalk, when the reflectance coefficients were measured to be -33 dB in both directions. Then, we have also implemented a bidirectional optical amplifier with two band splitters for the amplified bidirectional PON where the two different wavelength bands were allocated to the downstream and upstream signals transmission. In our measurement, we confirmed that the maximum gain of bidirectional optical amplifier with two band splitters could be increased to more than 30 dB owing to the efficient suppression of in-band crosstalk.