Silica-based Erbium-doped Fiber Research Articles

Flat-gain wide-band erbium doped fiber amplifier with hybrid gain medium

A new erbium-doped fiber amplifier (EDFA) is demonstrated using a combination of zirconia-based erbium-doped fiber (Zr-EDF) and silica-based Erbium-doped fiber (Si-EDF) as the gain medium. The EDFA comprises a 2 m long Zr-EDF and 9 m long Si-EDF optimized for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fiber Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

Flat-gain wide-band erbium doped fiber amplifier by combining two difference doped fibers

A new erbium-doped fibre amplifier (EDFA) is demonstrated using a combination of newly developed Erbium Zirconia co-doped fiber (Zr-EDF) and the commercial silica-based Erbium-doped fiber (Si-EDF) as the gain medium. Both fibers have a very high concentration of erbium ion. A compact amplifier operating in C-band region is firstly reported using a double-pass configuration. It is shown that average gains of the proposed Zr-EDF amplifier are obtained at approximately 18 dB with a gain variation of ±2 dB within C-band region. A flat-gain and wide band operation is achieved by configuring the amplifier in two stages comprising a 2 m long Zr-EDF and 9 m long Si-EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

COMPARATIVE STUDY ON SINGLE- AND DOUBLE-PASS CONFIGURATIONS FOR SERIAL DUAL-STAGE HIGH CONCENTRATION EDFA

A comparative study on a single- and double-pass co nfigurations for Erbium-doped fiber amplifier (EDFA ) are demonstrated using a gain media of high concentration Silica-bas ed erbium doped fiber (EDF). The amplifier has two stages comprising a 1.5 m and 9 m long EDF optimized for C-band and L-band operations respectively, in a single-pass and doubl e-pass configurations. The CFBG is used at the end of EDF stage to allow apropagation of signal and thus increases th e attainable gain in both C- and L-band spectra. At an input signal power of -30 dBm, a flat gain of 22 dB is achieved with a ga in variation of ±3 dB within a wide wavelength range from 1530 to 1600nm (C- and L-band) in double-pass configurations. The corresp onding noise figure varies from 4 to 8 dB within this wavelength region . The flat gains for single-pass configuration only amplify within 1555 nm to 1600 nm (L-band).

Experimental Investigation of Neutron Irradiation Effect on Silica-Based Erbium-Doped Fiber Amplifier

This paper studied the influence of neutron irradiation on the characteristics of 980nm pumped erbium-doped fiber amplifier(EDFA). After 7 days neutron irradiation, with the total fluence of 1.5×1013n/cm2, radiation induced loss changed little compared with pre-irradiation, maximum difference of single signal and WDM signal between pre-irradiation and post- irradiation are 0.5dB and 0.6dB, respectively. EDFA affected by neutron irradiation got less loss when the input signal power is higher.

OPTICAL AMPLIFIER WITH FLAT-GAIN AND WIDEBAND OPERATION UTILIZING HIGHLY CONCENTRATED ERBIUM-DOPED FIBERS

In this paper, we proposed a flat-gain and wide-band erbium doped fiber amplifier (EDFA) using two chirped fiber Bragg grating (CFBG) in serial configuration for double-pass operation. The amplifier consists of two sections of Erbium-doped fiber (EDF) operating in C-band and L-band respectively. A CFBG is used in each section to reflect the amplified signal back to the active area so that the overall gain spectrum can be enhanced and flattened. It is also observed that the gain of the amplifier produces a relatively higher gain with the Bismuth-based EDF (Bi-EDF) in the first stage compared to that of silica-based EDF (Si-EDF), especially in a longer wavelength region. The small signal gain of more than 19 dB is obtained within a wavelength region from 1545 to 1605 nm by the use of Bi-EDF with a small noise figure penalty. With a Si-EDF, the flat gain spectrum is observed within a wavelength region ranging from 1535 nm to 1605 nm with a gain variation of less than 2 dB at input signal of 0 dBm. This shows that the proposed serial double-pass amplifier may find its broad applications in wavelength division multiplexing long-haul systems as well as local optical networks.

Highly efficient short length Bismuth-based erbium-doped fiber amplifier

An efficient 21 cm Bismuth-based erbium doped fiber amplifier (Bi-EDFA) operating in both C- and L-band wavelength regions is proposed and demonstrated. The proposed Bi-EDFA uses the gain medium with an erbium ion concentration of 6300 ppm in conjunction with a double-pass configuration. Compared to conventional silica-based erbium-doped fiber amplifiers (Si-EDFAs) with the same amount of Erbium ions, the Bi-EDFA provides a higher attainable gain as well as a greater amplification bandwidth ranging from 1525 to 1620 nm. The proposed Bi-EDFA achieved a flat-gain of around 23 dB with gain variation of ±3.5 dB within the wavelength region from 1530 to 1565 nm at the maximum pump power of 150 mW. The corresponding noise figures are obtained at an average of 6 dB.

Towards the short-wavelength limit lasing at 1450 nm over 4I13/2 ? 4I15/2 transition in silica-based erbium-doped fiber

The transition rate of the stimulated emission at the higher energy levels of the excited states in a silica-based erbium-doped fiber can be enhanced by introducing fundamental-mode cutoff filtering mechanism. The electrons excited by optical pumping can more occupy the higher energy levels of the excited states when the transition rate for the lower energy levels (longer wavelengths) of the excited states is substantially suppressed. The achieved lasing wavelength can thus be moving toward the shorter wavelengths of the gain bandwidth. The laser transition between 4I13/2 ? 4I15/2 multiplets of the silica-based erbium-doped fiber is known to emit fluorescence with the shortest wavelength around 1450 nm. We, for the first time, experimentally demonstrate a widely tunable fiber laser at the wavelength very close to 1450 nm by using a standard silica-based C-band erbium-doped fiber. The tuning range covers 1451.9-1548.1 nm, with the best temperature tuning efficiency as high as 57.3 nm/ degrees C, by discretely introducing tunable fundamental-mode cutoff tapered fiber filters along a 16-m-long erbium-doped fiber under a 980 nm pump power around 200 mW. The signal-ASE-ratio can be higher than 45 dB whereas the FWHM of the laser lasing lights can be reduced below 0.2 nm by using an additional Fabry-Perot filter.

Study on the dynamics of a gain spectral hole in silica-based erbium-doped fiber at 77 K

A study on the dynamics of gain spectral hole burning (GSHB) in a silica-based erbium-doped fiber amplifier at 77 K was performed. When a saturation signal was input into an Er3+-doped fiber, a multigain spectral hole structure that consisted of nine gain spectral holes, was observed in the wavelength region from 1510 to 1640 nm at 77 K. As for the Er3+ ion concentration dependence of these gain spectral holes, the depth of the gain spectral hole at around 1530 nm was found to become shallower in the silica-based erbium-doped fiber that had higher Er3+ ion content. This Er3+ ion concentration dependence of the gain spectral hole depth suggests that the contribution of the energy-transfer interaction between Er3+ ions excited to the Stark levels within the ^4 I_13/2 manifold plays an important role in the gain spectral hole formation at 77 K. As far as we know, this is the first report of the Er3+ ion concentration effect on the GSHB in the Er3+-doped fiber. The dynamics of GSHB is discussed in relation to the effect of energy transfer between Er3+ ions. In addition, the relation between gain spectral hole structure and the Stark energy structure of Er3+ ion is also discussed.

Gain-flattened extended L-band EDFA with 43 nm bandwidth suitable for high signal powers

This report presents a gain-flattened silica-based Erbium-doped fibre amplifier with a flattened amplification bandwidth of 43 nm with ±0.3 dB flatness. The operating wavelength range is from 1564.7 to 1608.3 nm at 13 dB gain and 20 dBm maximum output power. The noise figure is less than 8 dB for 7 dBm input power. The amplifier is designed to be used in a Raman amplified transmission systems. The outstanding gain flatness is attributed to the accuracy of the gain equalising filter based on the fibre Bragg grating technology.

High-gain hybrid amplifier consisting of cascaded fluoride-based TDFA and silica-based EDFA in 1458–1540 nm wavelength region

A hybrid optical fibre amplifier is described that consists of a fluoride-based thulium-doped fibre amplifier and a silica-based erbium-doped fibre amplifier connected in a cascade. The amplifier has a gain of more than 25 dB and a noise figure of less than 9 dB over a wide wavelength region of 1458–1540 nm.

Broad-band erbium-doped fiber amplifier with double-pass configuration

We demonstrate a broad-band silica-based erbium-doped fiber amplifier (EDFA) with double-pass configuration. The signal gain and noise figure are obtained more than 24 dB and less than 6 dB, respectively, for 1526-1562 nm and 1569-1605 nm. The same signal gain can be achieved with 53% less pump power and 45% shorter erbium-doped fiber length, compared to a conventional parallel type EDFA. Furthermore, the noise figure and power conversion efficiency are improved for the wavelength range.

Spectrally-efficient L-C band EDFA having a seamless interband channel region using sampled FBGs

We report a method and experimental demonstration for an L-C band silica-based erbium-doped fiber amplifier (EDFA) utilizing the entire wavelength range of both the L and C bands with no dead in between. Sampled fiber Bragg gratings (FBGs) are used to split the L and C bands, thereby providing amplification at many discrete wavelengths as well as a sharp transition between the two bands. Optical amplification with negligible power penalty is demonstrated within the interband zone using a 1.6-nm spacing between the highest C hand and lowest L band channels.

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.

Comparative study on temperature-dependent multichannel gain and noise figure distortion for 1.48- and 0.98-μm pumped EDFAs

Temperature dependence of multichannel gain flatness and noise figure (NF) was compared for different pump wavelengths of 1.48 and 0.98 /spl mu/m on silica-based erbium-doped fiber amplifiers (EDFAs) through measurement-based numerical simulation. Owing to its temperature sensitive pump emission cross section, the 1.48-/spl mu/m pumping showed greater temperature sensitivity (maximum 0.75-dB gain flatness distortion with 0.57-dB average gain level shift, 0.3-dB NF variation for 25/spl deg/C change) than the 0.98 /spl mu/m pumping (maximum 0.5-dB gain flatness distortion with 0.015-dB average gain level shift, 0.05-dB NF variation for 25/spl deg/C change). However, it was also found that distortion ripple spectra mainly coming from the changes of signal cross sections and asymmetric gain temperature dependence necessitate compensation techniques in the EDFA link, irrespective of pump wavelength.

Long-wavelength erbium-doped fiber amplifier gain enhanced by ASE end-reflectors

We use for what we believe is the first time narrow-band end-reflectors to reduce losses through short-wavelength amplified stimulated emission (ASE) in silica-based erbium-doped fiber amplifiers operating at wavelengths above 1570 mm. The end-reflectors feed a small fraction of the ASE, up to a few tenths of a milliwatt, back into the amplifying fiber. The reflected ASE compresses the short-wavelength gain and thus reduces the ASE-losses, from, e,g., 50 mW for a launched pump power of 110 mW at 980 nm without end-reflector to 10 mW with an optimized end-reflector. We investigate possible improvements of gain (around 5 dB) and output power (up to 17 mW), and the influence of the amount and wavelength of the feedback.

Low-noise, broadband Er 3+ -doped silicafibre amplifiers

A broadband, low-noise silica-based erbium-doped fibre amplifier with a wide amplification bandwidth of 70 nm and a low noise figure of < 5 dB has been developed, by employing a hybrid configuration and adjusting the length of the Er3+-doped silica fibres used in the amplifier.

Simulation of 64 x 2.5 Gb/s WDM transmission over 1056 km of standard single-mode fiber using gain-flattened silica-based EDFAs

Using computer simulation, we have shown the viability of 64 2.5-Gb/s wavelength-division multiplexing (WDM) channel transmission over 1056 km of standard single-mode fiber (SMF) using gain-flattened silica-based erbium-doped fiber amplifiers (EDFAs), long-period fiber grating filters, and dispersion compensation.

1420-km transmission of sixteen 2.5-Gb/s channels using silica-fiber-based EDFA repeaters

Sixteen WDM channels each operating at 2.5 Gb/s mere transmitted through 1420 km of fiber without regeneration using silica-based erbium-doped fiber amplifiers. The amplifier spacings ranged between 96 km and 123 km. >

Thermal properties of an erbium-doped fibre amplifier

The influence of temperature on the absorption, fluorescence and small-signal gain characteristics of a silica-based erbium-doped fibre is investigated. The observed changes in the fluorescence and absorption spectra are found to be consistent with a Boltzmann-type redistribution of ion populations within the manifolds of the 4I13/2 : 4I15/2 transition. The influence of this behaviour on the gain characteristics of a cooled fibre amplifier is studied at two particular wavelengths: 1536 and 1553 nm. Significant improvements in amplifier performance are measured at both wavelengths when pumping into the 4I9/2 absorption band at liquid-nitrogen temperatures. The gain results are related to the absorption and fluorescence changes observed on cooling the fibre, and predictions of the importance of these results to device performance are made. The effect of cooling on the pump threshold performance of an erbium-doped fibre laser is also measured.