Radan Slavik

High-performance all-fiber Fabry-Perot filters with superimposed chirped Bragg gratings

The performance of large-band Fabry-Perot (FP) filters is investigated through numerical simulations and experimental realization. The limitations of the filters are studied theoretically to determine the impact of the chirped fiber Bragg grating (FBG) imperfections on spectral variations of the free spectral range (FSR), finesse, transmission loss, and polarization dependent loss (PDL). All-fiber FP devices are realized experimentally with finesse reaching 240 and covering a spectral band of 26 nm. For finesse up to 80, the filters present acceptable performance in terms of spectral variations of FSR (/spl plusmn/3%), finesse, attenuation (/spl plusmn/0.5 dB), PDL (<0.2 dB), and insertion loss (<3 dB).

Short multiwavelength fiber laser made of a large-band distributed Fabry-Pe/spl acute/rot structure

Multiwavelength fiber lasers are obtained by writing two superimposed chirped fiber Bragg gratings in a photosensitive Er/sup 3+/--Yb/sup 3+/ codoped optical fiber. The chirped gratings create a distributed Fabry-Pe/spl acute/rot structure in which the resonating fields of the different laser lines are spatially separated, thus, reducing cross-gain modulation. We demonstrate multiwavelength lasers emitting simultaneously over 8 and 16 lines spaced by 50 GHz. The active structure is very compact having a total active length of 8 cm. We discuss how the properties of the device are governed by the parameters of the chirped gratings giving high flexibility in the laser design.

Large-band periodic filters for DWDM using multiple-superimposed fiber Bragg gratings

The tight specifications of dense wavelength division multiplexing (DWDM) filters are challenging for any available technologies. In this letter, periodic transmission filters based on superimposed chirped fiber Bragg gratings are designed to have flat amplitude response and nearly constant in-band group delay. These filters should prove to be useful as interleavers and mux/demux filters in DWDM systems.

High-performance adjustable room temperature multiwavelength erbium-doped fiber ring laser in the C-band

Abstract Experimental realization of a high-power and highly uniform multiwavelength cw erbium-doped fiber ring laser with an intra-cavity frequency shifter and line spacing of 100 GHz is presented. The extremely flat response is achieved by optimizing the laser cavity losses, pump power and length of the active fiber. A simple method of shifting the laser emitting spectral region, which preserves the spectral output flatness, is demonstrated. The laser may be easily switched between two spectral regions of 1538–1548 and 1543–1559 nm. In both ranges, the power uniformity is better than 3 dB.

Frequency shift in a fiber laser resonator

A new model that describes the influence of a laser intracavity frequency shifter is proposed. Laser line broadening that is due to the presence of the frequency shift is derived. The theoretical model is validated by experimental results. Multiwavelength operation of this laser is explained.

Tunable dispersion and dispersion slope compensator using novel Gires-Tournois Bragg grating coupled-cavities

We report on the first realization of lattice-coupled all-fiber Gires-Tournois etalons for chromatic dispersion (CD) compensation. CD tunability is obtained by cascading two fiber Bragg grating superstructures. We show that the use of one superstructure with lattice-coupled cavities leads to a 60% tunability increase compared to single cavity designs. Dispersion slope compensation is proposed and demonstrated using a temperature gradient.

Multiwavelength 'single-mode' erbium doped fiber laser for FFH-OCDMA testing

A single-mode multiwavelength EDF laser was realized for the first time in a ring cavity configuration. The laser exhibited flat response over 10 nm, with line spacing of 100 GHz and output power of 10 dBm. The laser was used to test a FFH-OCDMA telecommunication system with a rate of 10 Gchip/s and an equivalent transmission rate of 125 Gbit/s. A strong reduction of beat noise was observed. The results clearly show that a multiwavelength laser source is needed for high data rate FFH-OCDMA systems.

(Sub-)Picosecond Flat-Top Waveform Generation using a Single Uniform Long-Period Fiber Grating

New and simple all-fiber method for generating flat-top optical pulses down to the sub-picosecond regime is proposed and demonstrated. A 600-fs Gaussian pulse is re-shaped into a 1-ps rectangular pulse with 20% energetic efficiency.

All-Fiber Ultrafast Second-Order Differentiator Based on a Single Uniform Long-Period Fiber Grating

We report the first experimental demonstration of an all-fiber higher-order optical differentiator. It is based on a single long-period fiber grating and allows processing of arbitrary waveforms with sub-picosecond time features.

Energetically-Efficient Sub-Picosecond Flat-Top Waveform Generation Using Long-Period Fiber Grating

Recently-reported filtering technique for ultrafast flat-top optical pulse re-shaping based on long-period fiber grating is demonstrated to generate pulses of sub-picosecond duration (800fs shown here) with unprecedented energetic efficiencies of almost 60%.