Haeyang Chung

A detailed experimental study on single-pump Raman/EDFA hybrid amplifiers: static, dynamic, and system performance comparison

This paper presents an experimental study on the performance comparison of three different schemes of single-pump dispersion-compensating fiber (DCF)-based Raman/erbium-doped fiber amplifier (EDFA) hybrid amplifiers together with a DCF-based Raman-only amplifier in terms of static properties, dynamic properties, and system impact: Raman-only amplifier (Type I), Raman/EDFA hybrid amplifiers recycling residual Raman pump in a cascaded EDF located either after (Type II) or prior to (Type III) a DCF, and a Raman-assisted EDFA (Type IV), the concept of which was proposed by Kurosawa et al. With respect to the overall gain and system impact based on bit error rate (BER) measurements in a transmission system, the hybrid amplifier of Type II was found to have the best performance among the four types while the Raman-only amplifier shows the best tolerance to transient response.

Dispersion-compensating Raman/EDFA hybrid amplifier recycling residual Raman pump for efficiency enhancement

We experimentally demonstrate a novel concept of the dispersion-compensating Raman/erbium-doped fiber amplifier hybrid amplifier recycling residual Raman pump for increase of overall power conversion efficiency. The proposed dispersion-compensating hybrid amplifier system has only one pump source for Raman amplification in the dispersion-compensating fiber (DCF) and the residual pump power after the DCF is recycled for secondary signal amplification in an erbium-doped fiber cascaded to the DCF. Using the proposed scheme, we achieve the significant enhancement of both signal gain and effective gain-bandwidth by 15 dB (small signal gain) and 20 nm, respectively, compared to the performance of the Raman-only amplifier.

Raman amplifier-based long-distance remote, strain and temperature sensing system using an erbium-doped fiber and a fiber Bragg grating

We demonstrate a novel, Raman amplifier-based long-distance sensing system for simultaneous measurement of temperature and strain using a combined sensing probe of an erbium-doped fiber (EDF) and a fiber Bragg grating. By recycling residual Raman pump power for generation of amplified spontaneous emission in the EDF after distributed Raman amplification in the transmission fiber, the overall system configuration was significantly simplified without requiring any additional broadband light source. We obtain a remote sensing operation of simultaneous temperature and strain measurement at a location of 50 km. High quality of sensing signals with a ~ 11 dB signal-to-noise ratio (SNR) is readily achieved even after the 50 km transmission with distributed Raman amplification.

High

We experimentally demonstrate the combined use of an ultrabroadband, incoherent, continuous-wave (CW) supercontinuum (SC) and a dispersion-profiled fiber to implement a photonic microwave filter with a -factor as high as 140. In our scheme based on spectrum slicing, such a high -factor can be readily achieved due to the following two reasons. The -factor restriction due to the limited wavelength tap number caused by narrow spectral bandwidth of conventional optical broadband sources can readily be solved owing to the ultrabroad bandwidth of the CW SC source. Second, the delay medium based on dispersion-profiled fiber compensates the nonuniform relative time delay between each wavelength filter tap caused by inherent wavelength chirping of conventional frequency domain multichannel comb filters. A fiber dispersion profile is provided for the nonuniform relative time delay compensation.

Q

We show experimental performance comparison of three types of single-pump highly efficient dispersion-compensating Raman/erbium-doped fiber amplifier (EDFA) hybrid amplifiers with respect to gain, noise figure (NF), and stimulated Brillouin scattering (SBS)-induced penalty: Raman/EDFA hybrid amplifiers recycling residual Raman pump in a cascaded erbium-doped fiber located either after (Type I) or prior to (Type II) a dispersion-compensating fiber, and a Raman assisted EDFA (Type III). Type I shows high small-signal gains, moderate large-signal gains, moderate NFs, and high SBS tolerances. Type II shows high small-signal gains, low NFs, and low SBS tolerances. Type III shows moderate small-signal gains, high large-signal gains, moderate NFs, and high SBS tolerances.

Microwave Filter Using Incoherent, Continuous-Wave Supercontinuum and Dispersion-Profiled Fiber

We experimentally demonstrate a simple and novel scheme for tunable real-repetition-rate multiplication, based on the combined use of fractional Talbot effect in a linearly tunable chirped fiber Bragg grating (FBG) and cross-phase modulation (XPM) effect in a nonlinear optical loop mirror (NOLM). By tuning the group-velocity dispersion of the chirped FBG fabricated with the S-bending method using a uniform FBG, we obtain high quality pulses at pseudorepetition rates of 20/spl sim/50 GHz from an original 8.5-ps 10-GHz soliton pulse train. We subsequently convert this pseudorate multiplication into a real-rate multiplication using XPM effect in an NOLM. A wavelength tuning is also achieved over a /spl sim/15-nm range.

Performance comparison of various configurations of single-pump dispersion-compensating Raman/EDFA hybrid amplifiers

An alternative photonic-generation scheme of ultrawideband (UWB) doublet pulses based on a semiconductor electroabsorption modulator (EAM) is proposed. The use of EAMs for doublet pulse generation has not been reported due to the difficulty of producing a U-shaped electrical-to-optical (E-O) transfer function. It is shown in the study that the creation of a U-shaped E-O transfer function from multi-quantum-well-based EAMs can be easily done under special conditions. An experiment is subsequently conducted to demonstrate the successful generation of UWB doublet pulses. The system performance of the generated UWB doublet pulses is then evaluated through a range of signal transmission experiments over a fiber/wireless transmission link. Error-free UWB doublet signal transmission is demonstrated.

Wavelength and repetition rate tunable optical pulse source using a chirped fiber Bragg grating and a nonlinear optical loop mirror

We experimentally compare the performance of our proposed single pump, Raman/EDFA hybrid amplifiers recycling residual Raman pump in a cascaded EDF located either after or prior to a DCF with that of a Raman assisted EDFA, the concept of which was proposed by Y. Kurosawa et al. (Proc. European Conf. on Optical Comm. ECOC2003, Tu3.2.5, 2003) in terms of gain, NF, nonlinearity, and BER.

Ultrawideband Doublet Pulse Generation Based on a Semiconductor Electroabsorption Modulator and Its Distribution Over a Fiber/Wireless Link

A novel, Raman amplifier-based long-distance sensing system using a combined sensing probe of an erbium-doped fiber (EDF) and a fiber Bragg grating is proposed for simultaneous measurement of temperature and strain. By recycling residual Raman pump power for generation of amplified spontaneous emission in the EDF after distributed Raman amplification in the transmission fiber, the overall system configuration was significantly simplified without requiring any additional broadband light source. A remote sensing operation of simultaneous temperature and strain measurement is obtained at a location of 50 km. High quality of sensing signals with a ~ 11 dB signal-to-noise ratio (SNR) is readily achieved even after the 50 km transmission with distributed Raman amplification.