Je-Myung Jeong

Effectively tunable dispersion compensation based on chirped fiber Bragg gratings without central wavelength shift

A systematic method of tunable dispersion compensation based on chirped fiber Bragg gratings (CFBGs) without a center wavelength shift will be proposed. The specially designed mechanical rotator can flexibly control the chirping ratio along the fiber gratings and consequently the group delay. The group delay can be linearly controllable since the proposed method can induce the linear strain gradient with the rotation angle change. The dispersion value can be effectively controlled in the range from -495.5 to -1406.0 ps/nm corresponding to the rotation angle. The resonant wavelength shift of CFBG is less than 0.03 nm over the dispersion tuning range. The theoretical analysis of the tuning mechanism based on the proposed method will also be discussed.

Improvement of catastrophic optical damage (COD) level for high-power 0.98-μm GaInAs-GaInP laser

We investigate improvement of catastrophic optical damage (COD) level for Al-free 0.98-/spl mu/m ridge waveguide laser diodes (LDs) using the impurity induced layer disordering (IILD) process applied near the facets. The IILD is used for the purpose of forming transparent windows near both facets of the LDs utilizing its ability to increase bandgap energy of the GaInAs-GaInAsP strained quantum-well (QW) active layer. Improvement of the cod level by at least 1.65 times compared to the conventional LDs is obtained for the LDs with Si/sup +/ implantation followed by annealing at 900/spl deg/C for 10 min.

A broadband ring network: multichannel optical slotted ring

Abstract This paper presents a multichannel optical ring network for broadband integrated services. The network uses a multichannel architecture with wavelength division multiplexing (WDM) and photonic packet switching devices for its access mechanism. The electronic speed bottleneck is removed out of the ring, which allows utilization of the full bandwidth for the optical fiber transmission medium. For compatibility with B-ISDN, the network uses a similar cell structure to that of an ATM based cell with a slotted ring concept. Fiber optic delay line matched filters are used as a means of address detection at the destination nodes. The network architecture is described and a design of the optical switching node is presented. A novel technique is devised in order to measure the average transfer delay of a cell in the multichannel slotted ring network. The analytical results show an excellent agreement with simulation results over a broad range of parameters. The results show that the major part of the cell transfer delay is coming from the propagation delay from a source to a destination. It is also observed that the throughput characteristic of the network depends upon the aggregated transmission capacity of the network.

Spectral shape tunable band-rejection filter using a long-period fiber grating with divided coil heaters

We have developed a new type of tunable band rejection filter, which provides high spectral-shaping flexibility in a wide tuning range. The filter consists of a long-period fiber grating (LPFG) with divided coil heaters. Each of the divided coil heaters is controlled individually to adjust a temperature distribution along the LPFG and to modify the spectral shape of the LPFG filter. The tunable band rejection filter is demonstrated to function properly when applied as an erbium-doped fiber amplifier gain-flattening filter.

Differential measurement scheme for Brillouin Optical Correlation Domain Analysis

We newly propose and experimentally demonstrate a differential measurement scheme for Brillouin optical correlation domain analysis, where the difference between Brillouin gain spectra constructed by a normal and a phase-modulated Brillouin pump waves are analyzed to measure local Brillouin frequencies in optical fibers. In experiments, a five-fold enhancement in the spatial resolution is obtained compared to an ordinary BOCDA system under the same modulation parameters, as a result of the improved dynamic range by the suppression of background noises.

Study on the Fabrication Process of Polarization Maintaining Photonic Crystal Fibers and Their Optical Properties

In this paper, we describe the fabrication process and the characteristics of polarization maintaining photonic crystal fibers (PM-PCFs). The PM-PCF is fabricated by stack-and-draw method, i.e., stacking silica capillary tubes (making a PM-PCF preform) and drawing to optical fiber. Firstly, a PM-PCF preform is formed by stacking two kinds of capillary tubes around a solid silica rod and jacketing these stacked tubes with an outer silica tube (out-jacket tube). Later, the desired preform is drawn to a fiber in a high temperature drawing tower. We also compare the polarization properties such as polarization dependent loss, birefringence, and differential group delay of the fabricated PM-PCF with those of the conventional PANDA PM fiber.

Tunable Dispersion and Dispersion Slope Compensator Using Strain-Chirped Fiber Bragg Grating

We propose a tunable dispersion and dispersion slope compensator based on induced strain-chirp in a uniform fiber Bragg grating. A specially designed mechanical rotator concatenated with a metal beam with linear thickness variation along its height was used to induce a quadratic strain gradient along the grating. We successfully demonstrated the dispersion and dispersion slope change by adjusting the rotation angle and feasibility of dispersion and dispersion slope compensation at 160-Gb/s nonreturn-to-zero transmission by simulation

Linearly configured BOCDA system using a differential measurement scheme.

We experimentally demonstrate a linearly configured Brillouin optical correlation domain analysis (BOCDA) system enhanced by a differential measurement scheme. On-off control of the pump phase modulation with an intentional loss at the end of a fiber under test is applied for the acquisition of a Brillouin gain spectrum. This application leads to a four-fold enhancement of the spatial resolution and doubling of the measurement range in comparison with the former system under the same modulation parameters.

Bidirectional measurement for Brillouin optical correlation domain analysis

We propose and experimentally demonstrate a bidirectional measurement for Brillouin optical correlation domain analysis as a novel and simple way of the performance enhancement. Brillouin gain and loss spectra of two adjacent correlation peaks are simultaneously and independently analyzed by applying midpoint attenuation in a fiber under test, which doubles both the speed and the range of the distributed measurement.

Improvement of kink and beam steering characteristics of 0.98-μm GaInAs-GaInP high-power lasers utilizing channel ion implantation

We demonstrate a kink and beam steering free operation of 0.98-/spl mu/m GaInAs-GaInP high-power ridge waveguide (RW) lasers utilizing channel ion implantation. The ion-implanted regions along the both sides of the ridge effectively suppressed the excitation of higher order lateral modes, which causes beam steering and kink. The maximum power without beam steering and kink has been achieved over 250 mW for channel ion-implanted RW lasers with 1.8-3.7-/spl mu/m ridge width, compared to 120-mW maximum power without the channel ion implantation.