Joon Tae Ahn

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 gain-clamped erbium-doped fiber amplifier with improved noise figure and freedom from relaxation oscillation

All-optical gain clamping scheme of erbium-doped fiber amplifier (EDFA) based on partial reflection of amplified spontaneous emission (ASE) into the EDFA is proposed and successfully demonstrated by using a coarse wavelength division multiplexing coupler with a mirror as an ASE reflector. The proposed gain-clamped EDFA (GC-EDFA) has good gain clamping characteristics up to -12 dBm of input signal power with 1-dB gain reduction from a clamped gain of 21 dB. Thanks to noncavity structure of the proposed GC-EDFA the amplifier is free from relaxation oscillation and has 1-dB improved noise figure, compared to a previous GC-EDFA based on a ring-type optical cavity.

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.

Polymer wavelength channel selector composed of electrooptic polymer switch array and two polymer arrayed waveguide gratings

An all-polymer wavelength channel selector is proposed and fabricated using chip-to-chip bonding of 16-channel electrooptic polymer switch array between two polymer arrayed waveguide gratings for the first time to our knowledge. A low power penalty of 0.1 dB at 10 Gb/s shows its potential as a wavelength channel selector for a packet switching system. Further efforts, however, should be paid to improve upon the large insertion loss of about 28 dB and bias phase drift problem for the proposed polymer channel selector to be a practical device.

Two-stage reflective-type erbium-doped fiber amplifier with enhanced noise figure characteristics

We demonstrate a two-stage reflective-type erbium-doped fiber amplifier with enhanced noise figure characteristics by placing an optical circulator between two erbium-doped fiber segments. Compared to the previous one-stage reflective amplifier, the proposed two-stage reflective amplifier provides noise figure enhancement of more than 2 dB and relatively flat small signal gain characteristics.

Simple method to adjust polarization dependence in polymeric arrayed waveguide gratings

Polarization-dependent wavelength shift of a birefringent-polymeric arrayed waveguide grating (AWG) is found to be adjusted simply by controlling the thickness of the first upper cladding layer while forming the upper cladding by several sublayers. Polarization-dependent wavelength shift is reduced to 0.08 from 4.24 nm in a birefringent-polymeric 16 /spl times/ 16 channel AWG on a silicon substrate by this method.

PLC platform for bidirectional transceiver with wide multimode output waveguide to receiver

We present a new configuration of a thin-film-filter (TFF)-embedded planar-light-circuit platform for a bidirectional transceiver module to enhance a tolerance of the insertion loss to the positional deviation of the TFF, by using a wide multimode waveguide structure that guides a reflected light from the TFF to a photoreceiver. It is experimentally shown that the new scheme has a merit in a high tolerance to the positional deviation of the TFF, and that it maintains a considerably high optical isolation by a proper arrangement of waveguides.

Characterization of an ASE reflector-based gain-clamped erbium-doped fiber amplifier

We develop a simulation tool for an all-optical gain-clamped erbium-doped fiber amplifier (GC-EDFA) based on an amplified spontaneous emission (ASE) reflector and thoroughly verify its validity by comparing simulation data with experimental ones. We carry out simulation work as changing conditions like reflection ratio and bandwidth of the ASE reflector, EDF length, and pump power. From this work, we have an exact understanding about the gain clamping principle that a reflected ASE acts like an intensity reservoir against input signal intensity variation. In general, as a reflected ASE power becomes higher, both a dynamic range and a noise figure (NF) increase; on the other hand, a clamped gain value decreases. The ASE reflector-based gain clamping scheme can be used for EDFAs with low NF characteristics at small input signal range in case a reflected ASE power is set at a level much lower than powers required for normal gain clamping function.

16-arrayed electrooptic polymer modulator

A 16-arrayed polymeric optical modulator is fabricated using an electrooptic (EO) polymer with a large EO coefficient and good thermal stability. The 16-arrayed modulator has lumped-type electrodes with a response time of less than 1 ns. The 16-arrayed modulator has good uniform modulation characteristics between the individual modulators. The deviation of half-wave voltages is 0.2 V and that of insertion losses about 1 dB. Crosstalks range from -28 to -36 dB and extinction ratios are more than 21 dB.