S. Selvakennedy

Long-wavelength EDFA gain enhancement through 1550 nm band signal injection

Abstract An experiment on gain enhancement in the long band (L-band) is demonstrated. Gain at the L-band is relatively inefficient because the operating wavelengths are far from the peak emission band of erbium ions. Gain enhancement for the L-band is achieved by using a signal from the conventional band (C-band). The efficiency of gain enhancement is strongly determined by the absorption coefficient of the C-band signal. Gain enhancement as high as 5.3 dB is obtained at −15 dBm of 1535 nm injected signal. Maximum gain enhancement for other injected signal wavelengths can be optimised by varying their power. Noise figure penalty is measured to be less than 1.0 dB at its optimised power. Furthermore, there is no penalty on the noise figure for injected signals longer than 1545 nm.

High-gain bidirectional Er/sup 3+/-doped fiber amplifier for conventional- and long-wavelength bands

High average gains of greater than 31 dB have been obtained between 1530-1560 nm (conventional-wavelength band, C-band) and 1570-1600 nm (long-wavelength band, L-band) using a saturating tone technique that represents 64 channels of a wavelength division multiplexed system. A bidirectional amplifying stage is utilized as high-power C-band and low-noise L-band stages. Noise figures of less than 3.6 and 5.4 dB are measured for the C- and L-bands, respectively.

Design optimisation of erbium-doped fibre ring laser through numerical simulation

Erbium-doped fibre ring laser is modelled, incorporating the effects of ion pairs, using the propagation and rate equations of a homogeneous, two-level medium. The numerical model has been obtained by developing a spectral analysis of erbium-doped fibre amplifiers. This approach is modified to account for the cyclical propagation of the field in the ring laser. Numerical simulations provide interesting information on the spectral behaviour as well as important parameters for device analysis and design, mainly the lasing wavelength and output power.

All optical gain-locking in erbium-doped fiber amplifiers using double-pass superfluorescence

All optical gain-locking in an erbium-doped fiber amplifier (EDFA) is demonstrated. A double-pass superfluorescence is created by using a broad-band fiber reflector centered at 1530 nm at the output of the EDFA, to lock the gain at 21 dB. Experiments on an eight-channel wavelength-division-multiplexing system shows promise with gain variation between channels of less than 0.6 dB over the input signal power range. While, gain variation with input signal power is about 0.2 dB for all channels.

Gain-clamped fibre amplifier using an ASE end reflector

Abstract All-optical gain clamping in an erbium-doped fibre amplifier is demonstrated using a broadband fibre Bragg grating that reflects the amplified spontaneous emission centred at 1530 nm with a 14 nm bandwidth. Experiments on an eight-channel wavelength division multiplexing system show promise when the gain is clamped at 21 dB. Gain flatness is less than 0.6 dB across all channels and gain variation is about 0.2 dB over the input signal power range.

A novel design of bi-directional silica-based erbium-doped fibre amplifier for broadband WDM transmissions

A new method for a broadband amplification based on erbium-doped fibre amplifier was developed using only a single laser diode pumped at 1480 nm. A dual-stage amplifier was employed where the first stage provides simultaneous bi-directional amplification of conventional- and long-band signals. The utilisation of unused amplified spontaneous emission and remnant pump power from the first stage enables realisation of high gain for the long-band signals in the second stage. Amplification of wavelength division multiplexing systems (two and four channels) was successfully demonstrated with an average gain of 22 dB and a noise figure less than 7 dB.

Erbium-doped fiber ring laser cavity in transient and steady states studied by a numerical approach

An erbium-doped fiber ring laser is modeled by use of the standard propagation and rate equations of a homogeneous, two-level medium. A numerical model is obtained by development of a spectral analysis of erbium-doped fiber amplifiers. This approach is modified to account for the cyclical propagation of the field in the ring laser. Numerical simulations provide interesting information on the spectral behavior as well as important characteristics of the cavity, mainly the lasing wavelength and output power. The model also permits the study of competing modes’ gain and signal evolutions during the transient state of the ring laser cavity.

Effects of signal seeding on long-wavelength-band Er3+-doped fiber amplifiers

A study of gain improvement in the long-wavelength band (L-band) by a seeding signal from the conventional-wavelength band (C-band) is presented. The seeding signal reduces losses through am- plified spontaneous emission and supplies energy for L-band amplifica- tion in the underpumped region. Gain improvement is observed for a copumped configuration, where the L-band and seeding signal are co- launched together with minimal noise figure penalty when an optimized seeding signal is used. The seeding signal boosts the L-band gain profile in the underpumped region to the flat-gain profile with gain flatness of less than 1 dB. High flat-gain values of 24 dB with gain variation of less than 0.9 dB when a seeding signal at 1555 nm is applied to the L-band amplifier pumped by only 105 mW from a 980 nm pump laser. A gain improvement of 52 dB is obtained at 1580 nm with this architecture.

A novel design for broadband fiber amplifier

A new method for a broadband amplification based on an Er doped fiber amplifier was developed using only a single laser diode pumped at 1480 nm. A dual-stage amplifier was employed where the first stage provides simultaneous bi-directional amplification of conventional- and long-band signals. The utilization of unused amplified spontaneous emission and remnant pump power from the first stage enables realization of high gain for the long-band signals in the second stage. Amplification of wavelength division multiplexing systems (2 and 4 channels) was successfully demonstrated with an average gain of 22 dB and a noise figure less than 7 dB.

Saturation parameters of erbium doped fibre amplifiers

Saturation parameters including gain, input signal power and output power were studied for erbium doped fibre amplifiers (EDFA). Knowledge of these parameters will enable a better design of EDFAs for operation as a power amplifier. In this saturated regime, gain saturation is defined as the gain at 3 dB gain compression from the unsaturated gain for a specific fibre length and pump power. Therefore, the output saturation power, P/sub osat/, and input saturation signal power, P/sub isat/, are defined as the output power and input signal power at which gain saturation occurs. The effects of pump power and fibre length were also studied in this paper.