Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

A novel and simple technique, based on nonlinear polarization rotation (NPR) effect, to generate stable multiwavelength oscillations in an erbium-doped fiber laser is proposed and successfully demonstrated. The NPR effect effectively induced intensity- and wavelength-dependent loss to alleviate mode competition caused by homogeneous gain broadening in erbium-doped fibers. Up to 28-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved. The outputs had uniform power distributions, and the power fluctuation in each wavelength is smaller than 0.2 dB within a period of an hour.

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Stable and uniform multiwavelength erbium-doped fiber laser using nonlinear polarization rotation

We report on the generation of multi-wavelength dissipative soliton (DS) in an all normal dispersion fiber laser passively mode-locked with a semiconductor saturable absorber mirror (SESAM). We show that depending on the strength of the cavity birefringence, stable single-, dual- and triple-wavelength DSs can be formed in the laser. The multi-wavelength soliton operation of the laser was experimentally investigated, and the formation mechanisms of the multi-wavelength DSs are discussed.

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Multi-wavelength dissipative soliton operation of an erbium-doped fiber laser

The nonlinear effects in optical fiber occur either due to intensity dependence of refractive index of the medium or due to inelastic-scattering phenomenon. This paper describes various types of nonlinear effects based on first effect such as self-phase modulation, cross-phase modulation and four-wave mixing. Their thresholds, managements and applications are also discussed; and comparative study of these effects is presented.

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Nonlinear Effects in Optical Fibers: Origin, Management and Applications

We demonstrate a switchable dual-wavelength synchronously pulsed fiber laser Q-switched by graphene saturable absorber. Wavelength-resolved studies on the output Q-switched pulses show that despite of large wavelength spacing up to 26 nm, the two Q-switched pulses at each individual wavelength can be temporally synchronized with per-pulse energy up to ~ 70 nJ. Further experiments show that by adjusting the intracavity birefringence, dual-wavelength emission can be switched to another dual-wavelength operation regime with wavelength separation of 5.7 nm. Our experimental results are also qualitatively supported by the cavity linear transmission characteristics of the ring cavity.

Switchable Dual-Wavelength Synchronously Q-Switched Erbium-Doped Fiber Laser Based on Graphene Saturable Absorber

We demonstrated a simple technique to obtain stable room temperature multiwavelength lasing in an erbium-doped fiber laser by the inhomogeneous loss mechanism. Successful reduction of the cross-gain saturation in erbium-doped fiber was achieved by incorporating a section of highly nonlinear fiber (HNLF) and a Fabry-Perot filter (FPF) in the laser cavity. More than 70 wavelengths simultaneous lasing were observed with the same frequency space of 25GHz. The laser had a total output power of ~3.2dBm, a bandwidth of 0.012nm (~1.5GHz) and a signal-to-spontaneous-noise ratio of ~44dB. Furthermore, the total output power can be increased to more than 190mW by moving the output port right after the EDFA.

Multiwavelength erbium-doped fiber laser based on inhomogeneous loss mechanism by use of a highly nonlinear fiber and a Fabry-Perot filter.

We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

A clock extraction scheme was demonstrated using an optoelectronic oscillator from high-speed nonreturn-to-zero (NRZ) signal A theoretical model on the locking range of the oscillator was presented A 10-GHz clock with a timing jitter of 04 ps was extracted from 10-Gb/s NRZ signal and a locking range of 800 kHz was achieved NRZ to return-to-zero (RZ) data format conversion was also performed simultaneously with the NRZ clock extraction

Clock extraction using an optoelectronic oscillator from high-speed NRZ signal and NRZ-to-RZ format transformation

A simple technique, based on nonlinear polarization rotation, for the amplitude equalization of high repetition rate pulses generated from a rational harmonic mode-locked fiber ring laser was demonstrated. Amplitude equalized pulses at 10 GHz (the fourth rational harmonic) were obtained with a harmonic component suppression ratio up to 30 dB. A theoretical explanation was given in detail, which indicates that, after pulse amplitude equalization, the situation of unequal pulse spacing can be improved to a certain extend.

Theoretical and experimental study of pulse-amplitude-equalization in a rational harmonic mode-locked fiber ring laser

We demonstrate a stable multiwavelength actively mode-locked erbium-doped fiber laser at 10 GHz based on a dispersion cavity and nonlinear polarization rotation (NPR) effect. The dispersion cavity allows simultaneous multiple wavelengths to satisfy the round-trip condition and smooth wavelength tuning, while the NPR ensures the stable operation and supermode noise suppression. A simple model is developed to explore the optimal setting of the cavity. Simultaneous dual- and five-wavelength operation is experimentally investigated

Caiyun Lou

Papers

Multiwavelength erbium-doped fiber laser based on inhomogeneous loss mechanism by use of a highly nonlinear fiber and a Fabry-Perot filter.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

Clock extraction using an optoelectronic oscillator from high-speed NRZ signal and NRZ-to-RZ format transformation

Theoretical and experimental study of pulse-amplitude-equalization in a rational harmonic mode-locked fiber ring laser

Stable multiwavelength dispersion-tuned actively mode-locked erbium-doped fiber ring laser using nonlinear polarization rotation