Dong Sung Lim

Fiber link loss monitoring scheme in bidirectional WDM transmission using ASE-injected FP-LD

We propose and demonstrate a novel fiber link loss monitoring method for a wavelength-division-multiplexed (WDM) passive optical network. This method is based on the optical signal comparison between a reference amplified spontaneous emission signal and its reflection from an optical reflector. Therefore, we can calculate the link loss exactly and also measure the characteristics of upstream optical signals without suspending the in-service channels. Since this scheme does not use narrow-band wavelength-dependent components such as fiber Bragg gratings, it is cost-effective in implementation and maintenance within a real optical network. We experimentally demonstrate that the link quality of upstream signals as well as fiber link faults on all WDM channels can be monitored in real time

Generation of multiorder Stokes and anti-Stokes lines in a Brillouin erbium-fiber laser with a Sagnac loop mirror.

We have demonstrated a novel multiwavelength lasing scheme in which a Brillouin erbium-fiber laser with a Sagnac loop mirror and a metal-coated planar mirror were used. The Sagnac loop permitted the simultaneous presence of a stimulated Brillouin scattering (SBS) pump and Stokes lines within the loop and thus generated high-order Stokes and anti-Stokes waves through a four-wave mixing (FWM) process. A total of 34 lines of Stokes and anti-Stokes waves with 0.08-nm line spacing was generated through the SBS and FWM processes with 1.5-mW SBS pump power at 1561 nm and 80-mW erbium-doped-fiber pump power.

Pulse-amplitude-equalized output from a rational harmonic mode-locked fiber laser

We report, for the first time to our knowledge, the demonstration of amplitude equalization of high-repetition-rate pulses generated from a rational harmonic mode-locked Er-doped fiber laser. The output pulses are injected into another fiber laser with a nonlinear optical loop mirror. This scheme provides pulse-amplitude equalization up to the ninth rational harmonic mode-locked pulse train.

All-optical clock recovery from NRZ data of 10 Gb/s

We demonstrate successfully an all optical clock recovery scheme based on all-fiber devices from nonreturn-to-zero format data of 10 Gb/s with a stabilized asymmetric Mach-Zehnder interferometer and a mode-locked erbium-doped fiber laser. This all-optical clock recovery method will find application in ultrahigh-speed all-optical communication systems.

A stabilised fibre-optic Mach-Zehnder interferometer filter using an independent stabilisation light source

We have demonstrated a stabilised scheme of fibre-optic Mach-Zehnder interferometer-type optical filter for application in periodic wavelength dividing filters. The stabilised scheme is based on controlling one arm length of the interferometer with electronically fedback fibre stretcher and utilizes an independent control light source and a voltage amplifier. This filter turns out to be useful for optical inputs not only of discrete spectra but also of broadband spectra. The output characteristics including stability, extinction ratio and transmission period are discussed.

10 and 20 GHz optical combs generation in Brillouin/erbium fiber laser with shared cavity of Sagnac reflector

A novel operation scheme of a Brillouin/erbium fiber laser (BEFL) whose cavity consists of two metal-coated fiber planar mirrors (FPMs) and a Sagnac reflector is presented. Optical comb generation of both 10 and 20 GHz spacings is demonstrated by discrimination of the even order Stokes waves and the odd order Stokes waves. Theoretical analysis based on the reflection properties of the Sagnac reflector yields a good description of the multi-wavelength BEFL characteristics.

A novel intra-cavity for efficient cascaded Raman generation using WDM couplers

A novel intra-cavity with a broadband spectral response is designed and demonstrated to deliver a 4th order Stokes cascaded Raman generation. A large transmission bandwidth of 295 nm is realized using the two WDM couplers. The results applied to a Raman fiber laser operating at 1706 nm wavelength using a 1313 nm pump source are reported.

Dual-wavelength cascaded Raman fiber laser

We have investigated the characteristics of a dual-wavelength cascaded Raman laser based on a composite resonator configuration using a fiber WDM coupler and two pairs of fiber Bragg gratings. The WDM coupler, which served to form a ring cavity and acted as an output coupler simultaneously, made the laser system simple and effective. Since the WDM coupler is made by the fused biconical taper technique and has the characteristic of periodic transmission windows, it can be designed to resonate at wavelengths corresponding to high odd Stokes orders simultaneously.

All-optical demultiplexing scheme using an optical parametric loop mirror

We have successfully demonstrated a novel all optical demultiplexing scheme using a optical parametric loop mirror. The scheme provides a demultiplexed output based on the FWM beam generation and well separated from the input signal and pump waves without an optical filter.

Continuously tunable multi-wavelength transmission filter based on a stabilised fibre-optic interferometer

Abstract We report the first successful demonstration, to our knowledge, of a continuously tunable multi-wavelength transmission filter based on environmentally stabilised fibre-optic Mach–Zehnder interferometer. The tunable scheme was achieved with a fine wavelength control through operating temperature adjustment of 1.3-μm laser diode used as light source for the stabilisation scheme. The transmission wavelength of the filter varied linearly with respect to the wavelength change of the stabilisation light source. The overall tuning range and the tuning sensitivity of the transmission wavelength of the tunable filter have been observed to be mainly dependent on those of the stabilisation light source itself.