Broadband Erbium-doped Fiber Amplifiers Research Articles

Design of broadband erbium-doped fiber amplifier using very high-speed integrated circuit hardware description language for next-generation optical network

We mainly concentrate on the problem of gain broadening and flattening of erbium-doped fiber amplifier (EDFA) using dual forward-pumping configuration in which we use pumping both at 980 and 1480 nm wavelengths. The gain cascading of two EDFAs pumped separately at 980 and 1480 nm combines the advantage of high gain characteristics of 980 nm pumping and broad bandwidth characteristics of 1480 nm pumping. The use of increased number of channels in the present dense wavelength division multiplexing (DWDM) optical network requires a flat gain spectrum across the whole usable bandwidth. The use of very high-speed integrated circuit hardware description language (VHDL-AMS) in lightwave system modeling has been explored. Its application in designing wideband EDFA has not been reported thus far. This work facilitates to design broadband EDFA operating in both the C-band and L-band regions with VHDL-AMS. The amplifier design is made of a dual stage, copumped at 980 and 1480 nm, which delivers an average output power of -16 dBm over the entire 3-dB bandwidth of 80 nm.

Demonstration of enhanced population feeding of the 1.53μm emitting level of Er3+ in TeO2–WO3–Li2O–P2O5 glasses using upconversion luminescence spectroscopy

P 2 O 5 is introduced into the Er3+-doped tungsten tellurite glasses to speed up the I11∕24-I13∕24 relaxation. The properties of infrared to visible upconverted luminescence as a function of P2O5 contents are studied to demonstrate the enhanced feeding rate of the 1.53μm emitting level of Er3+, which is in good agreement with that obtained using infrared emission spectra. The contributions of excited state absorption and cooperation energy transfer to the red and green upconverted luminescences are quantitatively evaluated. The Er3+-doped telluride glasses containing P2O5 could be a promising candidate as a host for broadband erbium-doped fiber amplifiers.

Broad-band EDFA gain flattening by using an embedded long-period fiber grating filter

An erbium-doped fiber amplifier (EDFA) gain flattening technique using an embedded long period grating (ELPG) is proposed. By bending the ELPG, due to different coupling strengths yielded from different bending curvatures, it can be used for both the static and dynamic gain flattening despite of the different pump currents of the EDFA. The experimental results demonstrate that the flattened gain region of 34nm can be achieved within 1dB ripple.

High-capacity undersea long-haul systems

This paper reviews technologies and techniques that have been used in deployed long-haul wavelength division multiplexing (WDM) systems and emerging technologies that could be used for the next generation of cost-reduced systems. The overview of current generation technologies starts with a discussion of modulation formats, focusing on the superior properties of the chirped return to zero on-off shift keying (CRZ-OOK) modulation format. The use of 10-Gb/s CRZ-OOK modulation format together with advanced fiber types, more powerful forward error correction (FEC), and broadband erbium-doped fiber amplifiers resulted in the deployment of dense WDM systems with capacities per fiber in terabits per second range and trans-Pacific reach. Demand for the systems with large design capacity led to further development of broadband optical amplifiers. Laboratory demonstrations successfully expanded transmission into the full C-band and later in the C and L transmission bands. The current market conditions dictate the need for reducing the first cost of an installed system rather than reaching record capacity per fiber. Reducing first cost can be achieved by reducing the amount of optical amplifiers in the cable by utilizing an excess performance margin provided by available RZ-OOK technology. Further improvements would be possible if more powerful FEC and modulation formats with better receiver sensitivity are used. For example, the RZ differential phase-shift keying (RZ-DPSK) modulation format with 3-dB better receiver sensitivity and better nonlinear tolerance to large amounts of accumulated dispersion is a very promising technology. This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ-DPSK signals versus RZ-OOK signals. Due to superior receiver sensitivity, the RZ-DPSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission

Optical properties of Er3+-doped telluride glasses with P2O5 addition for 1.5μm broadband amplifiers

In this paper, P 2 O 5 has been introduced into Er 3+ -doped telluride glasses. Emission and absorption spectra of the new glass are studied. It is observed that the nonradiative relaxation rate of 4 I 11/2 – 4 I 13/2 transitions and the 1.5 μm emission efficiency increases with the increase in P 2 O 5 content. The nonradiative relaxation rate of 4 I 11/2 – 4 I 13/2 transition in a glass with 7 mol% P 2 O 5 is four times greater than that without P 2 O 5 . The P 2 O 5 additives can also increase the thermal stability of the telluride glass. The present results indicate that telluride glasses with P 2 O 5 addition may be a promising candidate medium for broadband erbium-doped fiber amplifiers.

Fabrication and emission properties of Er 3+/Yb 3+ codoped tellurite glass fiber for broadband optical amplification

Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A new single mode Er 3+/Yb 3+ codoped tellurite fiber with D-shape cladding geometry is fabricated in this work. When pumped at 980 nm, a broad erbium amplified spontaneous emission (ASE) nearly 100 nm in the wavelength range of 1450–1650 nm around 1.53 μm is observed. It was found that the emission spectrum from erbium in tellurite glass fibers is almost twice as broad as the corresponding spectrum in tellurite bulk glass. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of about 2.3 mW from Er 3+/Yb 3+ codoped tellurite fiber ASE source is obtained under the pump power of 700 mW. The broad 1.53 μm emission of Er 3+ in Er 3+ /Yb 3+ codoped tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers.

Thermal stability and spectral properties of Er3+-doped gadolinium borosilicate glasses

Abstract A new glass of Gd 2 O 3 –B 2 O 3 –SiO 2 –Na 2 O–Er 2 O 3 system is prepared and the formation range of the glass is experimentally obtained. Excellent thermal stability of the glass has been demonstrated using differential thermal analysis. Effects of the B 2 O 3 content on the infrared spectral properties such as the 1.5 μm emission bandwidth and the Judd–Ofelt parameter Ω t ( t = 2, 4, 6) of Er 3+ ions in the glass has been observed. The glass exhibits a large integrated emission cross sections for the 1.5 μm emission band. The Er 3+ -doped gadolinium borosilicate glass is a great candidate for broadband erbium doped fiber amplifiers.

Wide-Band Two-Stage Erbium-Doped Fiber Amplifier Module in Parallel Configuration

We propose and experimentally demonstrate a two-stage broadband erbium-doped fiber amplifier module with a coupled structure over a gain bandwidth of 1520 to 1600 nm. As a result, 35.4 and 38.1 dB peak gains can be achieved at 1532 and 1568 nm, respectively, over the operation range. This proposed amplifier can also be used as a broadband amplified-spontaneous-emission light source.

Fabrication and amplified spontaneous emission spectrum of Er 3+-doped tellurite glass fiber with D-shape cladding

Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A single-mode Er 3+-doped tellurite glass fiber with D-shape cladding was fabricated in this work. The characterization of amplified spontaneous emission (ASE) from this newly fabricated Er 3+-doped tellurite fibers are exhibited. When pumped at 980 nm, a very broad erbium ASE nearly 150 nm around 1.53 μm is observed. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of 2 mW from Er 3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW. The broad 1.53 μm emission of Er 3+ in tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers.

Er3+ doped boro-tellurite glasses for 1.5 μm broadband amplification

B2O3 has been introduced in Er3+-doped tellurite glasses in order to increase their phonon energy and the multiphonon relaxation rate of the Er3+:4I11/2 → 4I13/2 transition, which will allow efficient 980 nm pumping. The inclusion of additional glass components such as GeO2 and Al2O3 has been shown to enhance the thermal stability of the boro-tellurite glasses. No crystallization peak (Tc) was observed in glass samples containing GeO2 and Al2O3. The suitability of these boro-tellurite glasses as host for broadband erbium-doped fiber amplifiers and their advantages over the other tellurite glasses are discussed.

Effect of Bi_2O_3 on the spectroscopic properties of erbium-doped bismuth silicate glasses

The spectroscopic properties of erbium-doped silicon dioxide, bismuth oxide, and sodium oxide glasses are investigated based on Judd–Ofelt analysis for absorption spectra, bandwidth analysis for emission spectra, and lifetime measurements of the 4I13/2 level of Er3+. The effects of bismuth oxide on these three optical parameters are discussed in terms of the local basic nature of the glass, of variations in ligand fields about Er3+ sites, and of the phonon energy and the refractive index of the glass host, respectively. The data obtained suggest that bismuth oxide does not have a promising composition for use with a broadband erbium-doped fiber amplifier.

Optical fiber amplifiers for WDM optical networks

In recent years, tremendous progress has been made in the development of broadband erbium-doped fiber amplifiers (EDFAs), which form the backbone of high-capacity lighwave communication systems. Initially, the use of gain equalization filters increased the bandwidth of amplifiers by a factor of three (relative to first-generation amplifiers deployed in the field). Subsequently, the introduction of a two-band architecture, which includes amplifier sections for the C-band and the L-band, resulted in a further doubling of the bandwidth. In addition, this amplifier provides high output power and low noise figure to support the ever-increasing capacity demand on lightwave systems. Commercial systems with up to 80 wavelength division multiplexing (WDM) channels having a total capacity of up to 400 Gb/s are currently available, and terabit systems have been demonstrated in the laboratory. The recently discovered phenomenon of fast power transients in chains of EDFAs constituting an optical network has been shown to impair the performance of propagating channels in the event of channel failure or network reconfiguration. Several schemes to control the gain of EDFAs have been devised to mitigate the degradation caused by the fast power transient effect. Practical broadband amplifiers incorporating these and other control schemes, such as internal attenuation to control gain tilt, will enable future terabit and higher capacity networks.

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.

Broad-band erbium-doped fiber amplifier flattened beyond 40 nm using long-period grating filter

Broad-bandwidth amplification is essential for the construction of high-capacity multichannel communication systems. We describe a silica-based erbium doped fiber amplifier (EDFA) with a flat gain bandwidth exceeding 40 nm. The dual-stage EDFA includes a precisely designed inter-stage long-period fiber grating filter with more than 14-dB peak attenuation. By careful choice of the filter spectrum and fiber lengths, this EDFA is flat to within 1 dB over 40 nm while producing a noise figure below 4.0 dB and nearly +15-dBm output power.