Mode-locked Erbium Research Articles

Actively mode-locked erbium fiber ring laser using a Fabry–Perot semiconductor modulator as mode locker and tunable filter

A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a Fabry–Perot semiconductor modulator. The modulator played the simultaneous roles of an intensity mode locker and a tunable optical filter. Stable single- or dual-wavelength nearly transform-limited picosecond pulses at gigabit repetition rates were generated. Continuous wavelength tuning was achieved by simply controlling the temperature of the modulator. Pulse train with a repetition rate up to 19.93 GHz (eight times the driving frequency) was obtained by using rational harmonic mode-locking technique.

A Polarization-Maintaining and Dispersion-Managed 10-GHz Mode-Locked Erbium Fiber Ring Laser Providing Both sech2- and Gaussian-Shaped Pulses

We have constructed a polarization-maintaining and dispersion-managed 10-GHz regeneratively mode-locked Erbium fiber ring laser which generates highly stable and nearly transform-limited 3.5- to 7-ps sech2pulses at 1560 nm. By forcing the wavelength to a narrow-band ripple in the transfer function of the laser in-line filter, highly stable 15-ps Gaussian-like pulses were also obtained. We have studied in detail the temporal and spectral shapes of the pulses and confirmed a good agreement with the corresponding theoretical fits for transform-limited sech2and Gaussian pulses, respectively. The pulses have a timing jitter below 0.2 ps and the highest reported supermode noise suppression of 90 dB. This remarkably high supermode noise suppression is likely a result of the dispersion-management in the laser cavity. The wavelength is tunable within 1530–1570 nm. The laser has excellent long-term stability and is very robust to thermal and mechanical disturbances.

A passively mode-locked fibre laser with a delayed optical path for increasing the repetition rate

We propose a delayed optical path (DOP) scheme to increase the repetition rate of a passively mode-locked erbium fibre laser. The time interval between adjacent pulses from a passively mode-locked fiber laser with a DOP is shortened from the round trip time of the laser cavity to the time difference between the DOP and the corresponding original path in a part of the cavity. The detail of the operational principle of the DOP scheme and its experimental demonstration at the 5th harmonic frequency of the fundamental repetition rate are reported.

Broadband square-pulse operation of a passively mode-locked fiber laser for fiber Bragg grating interrogation

A long-cavity, passively mode-locked erbium fiber laser operated in the square-pulse regime is demonstrated as a useful light source for interrogating fiber Bragg grating arrays. Output pulses with 4-W peak-power, 10-ns pulse widths, and bandwidths greater than 60nm were used successfully to interrogate 2% fiber Bragg gratings.

Active harmonic modelocking of an erbium fiber laser with intracavity Fabry-Perot filters

We present both experimental and theoretical investigations of the operation of a harmonically modelocked erbium fiber ring laser stabilized by an intracavity bit-rate etalon. Our model analyzes the effects of cavity components and operating parameters on laser stability and output pulse characteristics. The model predicts the output pulsewidth variation with laser cavity parameters such as cavity length, dispersion, and finesse of intracavity Fabry-Perot etalons. If the laser cavity length is not optimized, a maximum 50% increase in pulsewidth can occur at 5 Gb/s pulse rate. A repetition rate etalon with a finesse of 50 is sufficient to provide a side-mode suppression ratio of over 50 dB in the laser output. We also discuss how detuning from the optimal modulation frequency increases the excess noise that affects the laser stability. The theory predicts a maximum detuning range of /spl plusmn/100 kHz, which agrees with the experimental observations. These theoretical results can guide the design of similar lasers over a wide range of operating parameters.

10-GHz, 13-ps erbium fiber laser employing soliton pulse shortening

An actively mode-locked single-polarization erbium fiber laser modulated at 10 GHz utilizes intracavity soliton formation to produce 1.3-ps pulses, well below the Kuizenga-Siegman limit, without passive mode locking. The observed degree of pulse shortening agrees with the predictions of recently developed soliton laser models. The pulse dropout ratio was measured to be less than 10(-12), and the rms amplitude and phase jitter are less than 1.1% and 0.16 ps, respectively.

Synchronized mode-locked erbium fibre lasers with intracavity dispersion control using chirped in-fibre Bragg gratings

Abstract We demonstrate a dual-wavelength fibre laser system using chirped fibre Bragg gratings as reflectors and dispersive elements. The system produces two synchronized trains of soliton pulses with rms jitter of 620 fs.

Synchronized mode-locked erbium fibre lasers with intracavity dispersion control using chirped in-fibre Bragg gratings

We demonstrate a dual-wavelength fibre laser system using chirped fibre Bragg gratings as reflectors and dispersive elements. The system produces two synchronized trains of soliton pulses with rms jitter of 620 fs.

Amplitude Modulated Harmonic Mode-Locking Characteristics of Er3+ Doped Fiber Ring Laser.

In this paper, characteristics of amplitude modulated harmonically mode locked (AM-HML) erbium doped fiber (EDF) ring laser are presented. It is investigated that the AM-HML method can provide a precise control of the lasing spectral bandwidth. Which in turn, can control the nonlinear effects in single mode fibers, such as stimulated Brillouin scattering in optical fiber communications. The optical spectral bandwidth is found to be broadened from -5GHz to-16.6GHz when the AM modulating low harmonic signal frequency is varied from -3.1609MHz to -44.2526MHz (1 to 14 times of the fundamental cavity frequency fa) at a fixed pulse rate of fh 2.1241 GHz. The effect of the percentage of AM modulation depth is also studied and it is observed that the bandwidth of the AM-HML laser is slightly affected when the percentage of AM modulation is varied from -5% to -50%.

10 GHz, 2 ps regeneratively and harmonically FM mode-locked erbium fibre ring laser

A 10 GHz regeneratively and harmonically FM mode-locked erbium fibre ring laser is reported for the first time. The output pulse width is 2 ps and the spectral width is 1.4 nm, resulting in a time bandwidth product of 0.34. The output pulse is almost transform limited, despite the FM mode-locking. This can be attributed to the anomalous group velocity dispersion which compensates for the up-chirping. The down-chirping does not evolve into stable FM mode-locking because it is reduced by the self phase modulation occurring in the long cavity.

Diode pumped high power simultaneously Q-switched and self mode-locked erbium doped fibre laser

The authors report for the first time a diode pumped, electro-optically Q-switched, self mode-locked erbium doped fibre laser. Simultaneous Q-switching and mode-locking produces 4 ns pulses of 540 W peak power in a 20 ns Q-switched envelope.

Performance characterization of a harmonically mode-locked erbium fiber ring laser

We describe the performance of a harmonically mode-locked, erbium fiber ring laser. Transform-limited pulses with durations of 20-50 ps at 5.044 GHz repetition rate are obtained. The modulation frequency can be detuned by up to /spl plusmn/70 kHz and the lasing wavelength can be varied over the entire erbium gain bandwidth. Pulsewidths and pulse bandwidths are measured as a function of modulation power and frequency detuning. The laser is actively stabilized by locking intra-cavity Fabry-Perot etalon passbands to the laser modes. >

High-power soliton fiber laser based on pulse width control with chirped fiber Bragg gratings

Chirped fiber Bragg gratings control the pulse width and energy in Kerr mode-locked erbium fiber soliton lasers. We create high-energy pulses by providing large amounts of excessive negative dispersion, which increases the pulse width while keeping the nonlinearity of the cavity constant. With a chirped fiber grating of 3.4-ps(2) dispersion, 3-ps pulses with an energy content higher than 1 nJ are generated at a repetition rate of 27 MHz. By controlling the polarization state in the cavity, we obtain a tuning range from 1.550 to 1.562 mu;m.

Ultrastable harmonically and regeneratively modelocked polarisation-maintaining erbium fibre ring laser

The authors report the operation of a harmonically and regeneratively modelocked erbium fibre ring laser at 1.55 µm for the first time. Harmonic regenerative modelocking was achieved by feeding back the harmonic longitudinal beat signal which was detected with a high speed photodetector and a high Q dielectric filter. The repetition rate was 10 GHz and the soliton effect shortened the pulse width from 7.0 to 2.7 ps.

Multisoliton interaction in actively mode-locked erbium fiber lasers: theory and experiment

We present a perturbative analysis of the interaction between three optical solitons in the presence of synchronous amplitude modulation and bandwidth limited amplification. We predict and experimentally observe the self-generation of sequences of interacting soliton pulses with a fixed temporal separation that circulate inside an actively mode-locked erbium-doped fiber ring soliton laser.

Soliton propagation without transmission control using a phase-locked erbium fibre ring laser

2.5 Gbit.s-1 solitons have been transmitted a distance of 17 600 km in a recirculating loop without transmission control. To achieve this a new stabilisation technique for modelocked erbium fibre lasers has been implemented. Cavity length changes are tracked with an electronic phaselock loop and the phase of the RF drive adjusted accordingly.

All-fiber source of 100-nJ subpicosecond pulses

Chirped pulse amplification of a stretched pulse passively mode-locked erbium fiber laser is demonstrated. The two-stage all-fiber amplifier system delivers 800-fs pulses with pulse energies up to 100 nJ at a repetition rate of 200 kHz.

Optically controlled wavelength-adjustable passively modelocked erbium-doped fibre ring laser

An integrated all-fibre technique has been used to implement wavelength tunability in a passively mode-locked erbium fibre ring laser. A smooth, continuous tuning range of 4 nm controlled simply by varying the power of an optical pump beam has been demonstrated.

Environmentally stable Kerr-type mode-locked erbium fiber laser producing 360-fs pulses

We demonstrate an environmentally stable Kerr-type mode-locked erbium fiber laser producing 360-fs near-bandwidth-limited pulses. Environmentally stable operation is possible in the presence of nonpolarization-maintaining fiber components provided that their overall length is short compared with the length of the polarization-maintaining fiber components. The pulses are generated at a stable repetition rate of 27 MHz and have an energy content of 60 pJ.

Novel method to suppress noise in harmonically modelocked erbium fibre lasers

A novel method to suppress noise in a high harmonic mode-locked erbium fibre laser is proposed and realised for the first time, dithering the cavity length at a kilohertz rate. This method makes only one supermode in the laser dominant and suppresses the others. A fibre laser so stabilised has enabled 2.5 Gbit/s soliton transmission over 205 km fibre remaining error free for 100 min, and in a recirculating loop achieving a 10/sup -9/ bit error rate at 12000 km, respectively. >