Broadband Amplified Spontaneous Emission Research Articles

Broadband ASE source for S + C + L bands using hafnia-bismuth based erbium co-doped fibers

A broadband amplified spontaneous emission (ASE) source is demonstrated experimentally by using hafnia-bismuth based erbium co-doped fibers (HB-EDFs) with a total length of 200-cm as an active medium. Both of parallel and series configurations are used to generate a broadband ASE source, operating at 1.5 µm and that cover S-, C-, and L-bands. The comparison proves that the series configuration provides a relatively larger ASE bandwidth, higher output power, higher efficiency, and lower complexity. At the optimum total pumping power of 280 mW, a broadband ASE source of 57 nm with a power ripple of ± 7.5 dB is achieved. Besides, a total ASE power of 20.8 mW is obtained, which is equivalent to 7% of the pumping efficiency.

Temporal and spectral coding over amplified spontaneous emission for secure optical coherent communications.

We demonstrate secure optical coherent communications employing low-coherence matched detection based on the randomness of amplified spontaneous emission (ASE) noise. Two-level physical-layer optical encryption is achieved through temporal and spectral coding over a broadband ASE source. An ASE-carried signal and unmodulated carrier are polarization multiplexed, transmitted over a same single-mode fiber (SMF), and separated with the aid of polarization tracking before having matched detection at the receiving side. The impact of chromatic dispersion on the low-coherence matched detection system is analyzed and experimentally investigated. We experimentally realize optically coded 20 Gbaud QPSK and 8-PSK signals transmission over a 43 km SMF span with a maximum line rate of 60 Gbits/s.

Enhanced Transmission Performance Using Backward-Propagated Broadband ASE Pump

We propose a novel first order incoherent broadband amplified spontaneous emission (ASE) pump which can be used as a seed pump in dual order backward-pumped distributed Raman amplification. Using this broadband ASE pump mitigates the relative intensity noise (RIN) transfer from the backward-propagated second order pump to the signal, and extends the reach of $10\times120$ Gb/s DP-QPSK WDM transmission to 7915 km, giving a minimum of 12% (833 km) increase, compared with using low RIN semiconductor laser diode and random distributed feedback fiber laser.

Enhancement on the generation of amplified spontaneous emission in thulium-doped silica fiber at 2 [formula omitted

This paper investigates the generation of the amplified spontaneous emission (ASE) from thulium-doped silica fiber pumped at 1570 nm and 793 nm. The developed model provides the ASE spectral power as functions of the fiber length and the pump power under single-pass forward (SPF) and double-pass bi-directional (DPB) pumping schemes. A broadband ASE source generated by solving a set of rate and propagation equations for 1570 nm and 793 nm pumping transitions, and taking into account the influences of cross relaxation (CR) in both pump schemes. Our findings reveal that for 1570 nm pumping scheme, CR transition reduces the ASE generation. In addition, longer fluorescent lifetime increases the ASE power and reduces the pump power threshold. We numerically enhanced the generation of ASE broadband source from 1570 nm/1570 nm DPB pumping scheme. Our results show that 1570 nm/1570 nm DPB produces broadband ASE source with high slope efficiency and broader spectral bandwidth than that in SPF configuration. As a result, a 1570 nm/1570 nm DPB pump scheme is a suitable configuration to obtain higher power efficiency and a wider broadband source for the chosen thulium-doped silica fiber characteristics.

2.53 kW all-fiberized superfluorescent fiber source based on a compact single-stage power-scaling scheme

In this paper we demonstrate an all-fiberized superfluorescent fiber source that has a maximal output power of 2.53 kW and is based on a single-stage power amplification configuration. The seed source is a broadband-amplified spontaneous emission source with a full output power of 27.6 W. A single-stage dual-clad fiber amplifier is used, in which the maximal optical-to-optical conversion efficiency is 81.47%. A beam quality of M2 = 1.53 is measured at an output power of 1 kW. At maximum output power, the central wavelength and full width at half maximum linewidth of the amplified light are 1082.08 nm and 6.32 nm, respectively. No conspicuous spike was observed at the stimulated Raman scattering wavelength. The corresponding power fluctuation is 2.97%, which indicates the good power stability of the broadband high-power superfluorescent fiber source (SFS) system. This kilowatt-class high-power all-fiberized SFS system which has high conversion efficiency and good power stability and is based on a compact single-stage power-scaling scheme, is an alternative and competitive solution for industrial precision processes and special stabilized pumping. To the best of our knowledge, this is the highest power SFS ever reported, and the first demonstration of a high-power SFS with a kW-level output power in a compact single-stage power-scaling scheme.

Compact broadband amplified spontaneous emission in Tm^3+-doped tungsten tellurite glass double-cladding single-mode fiber

We reported the ~2 μm amplified spontaneous emission (ASE) performance of highly Tm3+-doped (3.76 × 1020 ions/cm3) tungsten tellurite single-mode fibers. The double-cladding fiber was pumped by a commercial 792 nm laser diode without any reflectors. Broadband ASE spectra with the bandwidth (FWHM) varying from ~45 nm to ~140 nm were achieved in a fiber length of 34 cm. The maximum output power was ~34 mW, with a slope efficiency of 4.8%. The ASE beam quality factor (M2) was 1.8. The dependence of output power, ASE mean wavelength, and bandwidth on the launched pump power and fiber length were discussed in detail.

High-Power Broadband Thulium-Doped All-Fiber Superfluorescent Source at 2 $\mu{\rm m}$

We report on the experimental realization of a stable high-power all-fiber broadband amplified spontaneous emission (ASE) source at 1992 nm by using an MOPA configuration. The ASE source yields a maximum output power of 25 W with a slope efficiency of 49%, and the wavelength range spanned from 1930 to 2100 nm with a full-width at half-maximum bandwidth of 25 nm. In addition, we also measure the output power stability of the high-power broadband ASE source and a narrowband CW fiber laser with the same thulium-doped fiber main amplifier under incident pump power of 66 W. The output power fluctuation of the high-power broadband ASE source is below ±0.3%, which is much lower than that (±2.3%) of narrowband continuous wave thulium-doped fiber laser.

Wideband Spectrum-Sliced ASE Source Operating at 1900-nm Region Based on a Double-Clad Ytterbium-Sensitized Thulium-Doped Fiber

A wideband spectrum-sliced amplified spontaneous emission (ASE) source operating in 1900-nm region is demonstrated using a newly developed double-clad ytterbium-sensitized thulium-doped fiber (YTF) and a Sagnac loop mirror. The YTF used was drawn from a D-shape preform, which was fabricated using the modified chemical vapor deposition (MCVD) and solution doping technique. The YTF was pumped by a 980-nm multimode laser to generate an ASE at 1900 nm through the transition of thulium ion from 3F4 to 3H6 with the assistance of ytterbium to thulium ion energy transfer. The broadband ASE was spectral sliced by the loop mirror, which was constructed using a 3-dB coupler and a piece of polarization maintaining fiber (PMF). A wideband comb with channel spacing of 3.3 nm and an extinction ratio of 9 dB was achieved with a multimode pump power of 1 W within a wavelength range of more than 300 nm. The center of the comb spectrum was at 1888 nm with peak power of around -53 dBm.

High power narrow-band fiber-based ASE source

In this paper we describe a high power narrow-band amplified spontaneous emission (ASE) light source at 1030 nm center wavelength generated in an Yb-doped fiber-based experimental setup. By cutting a small region out of a broadband ASE spectrum using two fiber Bragg gratings a strongly constrained bandwidth of 12±2 pm (3.5±0.6 GHz) is formed. A two-stage high power fiber amplifier system is used to boost the output power up to 697 W with a measured beam quality of M2≤1.34. In an additional experiment we demonstrate a stimulated Brillouin scattering (SBS) suppression of at least 17 dB (theoretically predicted ~20 dB), which is only limited by the dynamic range of the measurement and not by the onset of SBS when using the described light source. The presented narrow-band ASE source could be of great interest for brightness scaling applications by beam combination, where SBS is known as a limiting factor.

Influences of ASE on the performances of Q-switched ytterbium-doped fiber lasers

The output characteristics of actively Q-switched ytterbium-doped fiber lasers (YDFL) are investigated in this paper. Our experimental results show that, the combined effect between the short switching time and the gain transient property of doped fiber causes the initial amplified spontaneous emission (ASE) power fluctuation, forming the multi-peak structure in the output pulse for either ring or linear cavity Q-switched YDFL. The pulse buildup time decreases with the rising of the pump. Moreover, since the broad-band ASE generated in the YDF is very high, it may saturate the doped fiber once the switch has been opened, making it difficult to achieve Q-switched laser oscillation for both fiber lasers. By using ASE filter to suppress the initial ASE, the gain supplied by the YDF can be greatly enhanced, which can not only decrease the threshold, but also greatly decrease the duration, and enhance the peak power of the Q-switched laser pulse as well. By using such an ASE filter, the Q-switched laser pulse with the peak power of 40.7 W and the duration of 30 ns has been achieved for the linear cavity YDFL pumped with 160 mW.

Broadband ASE source using bismuth-based erbium-doped fibers in double-pass set-up

Flat and broadband amplified spontaneous emission (ASE) spectrum, which covers both C and L-band regions is demonstrated. The ASE source employs 49 and 215 cm long Bismuth-based erbium-doped fiber (Bi-EDF) to provide C- and L-band amplifications, respectively as gain media in conjunction with double-pass linear configuration. The ASE power level obtained varies from -24 to -35 dBm within 85 nm bandwidth from 1530 to 1615 nm at the optimum pump powers combination. The total ASE power reaches up to 26 mW at maximum total pump power of 320 mW, which can be translated to 8% efficiency. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1636-1638, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25239

A broadband ASE light source-based full-duplex FTTX/ROF transport system

A full-duplex fiber-to-the-X (FTTX)/radio-over-fiber (ROF) transport system based on a broadband amplified spontaneous emission (ASE) light source is proposed and demonstrated for rural wide-spread villages. Combining the concepts of long-transmission transmission and ring topology, a long-haul single-mode fiber (SMF) trunk is sharing with multiple rural villages. Externally modulated baseband (BB) (1.25 Gbps) and radio-frequency (RF) (622 Mbps/10 GHz) signals are successfully transmitted simultaneously. Good bit error rate (BER) performance was achieved to demonstrate the practice of providing wire/wireless connections for long-haul wide-spread rural villages. Since our proposed system uses only a broadband ASE light source to achieve multi-wavelengths transmissions, it also reveals an outstanding one with simpler and more economic advantages.

Full-duplex ROF transport systems based on a broadband ASE light source and nonlinear distortion suppression scheme

A full-duplex radio-over-fiber (ROF) transport system employing a broadband amplified spontaneous emission (ASE) light source and nonlinear distortion suppression scheme is proposed and demonstrated. A 10 GHz/70 Mbps data rate (compatible WiMAX format) signal is externally modulated and transmitted over a 120 km single-mode fiber (SMF) transmission both for down/up-link. Good bit error rate (BER) performance and a clear eye diagram were achieved in our proposed systems. Such a proposed full-duplex ROF transport system is suitable for long-haul microwave optical links.

Loss budget in single-fiber loopback access networks with ASE light source considering gain compression effect of GS-SOA

This paper estimates the loss budget of wavelength division multiplexing (WDM) single-fiber loopback access networks that employ a broadband amplified spontaneous emission (ASE) light source at the central office (CO) and an optical modulator with optical amplification function in each optical network unit (ONU). This study considers the backreflection lights from two sources, a broadband ASE light from the CO (Reflection-I) and a modulated signal from the ONU (Reflection-II). A gain-saturated semiconductor optical amplifier (GS-SOA) is placed at the ONU to reduce the excess intensity noise of sliced ASE and the spontaneous-spontaneous beat noise caused by Reflection-II; this technique increases the loss budget of the transmission line and removes an optical pre-amplifier from the optical receiver. Experiments clarify that with the gain compression effect of the GS-SOA the loss budget is 22.7dB.

WAVELENGTH SELECTIVE AUXILIARY C-BAND ASE PUMPING FOR L-BAND EDFA

The variation of Gain and Noise Figure (NF) at 1580 nm with length of Erbium doped fiber (EDF) for two auxiliary pumping schemes employing narrowband Amplified Spontaneous Emission (ASE) and ASE filtered up to a particular wavelength in C-band, by considering a serially cascaded two stage wideband amplifier model are investigated. It is shown that indeed, there exists a wavelength range of ASE for achieving maximum gain. The gain can be increased by 14 dB if wavelength bandwidth of 1480–1554 nm is selected instead of pumping with the broadband ASE (1480–1700 nm). By auxiliary pump using ASE sliced in the 1533 nm window, gain as high as 28 dB and NF as low as 5.5 dB can be achieved for shorter fiber length. To achieve gain of 25–30 dB for the L-band signal only a EDF length of 30 m is required in the case of tuned ASE launching at 1533 nm as compared to 40 m and 65 m by optimized ASE bandwidth and broadband. The values of noise figure do not show significant variation in any of the three configurations. It is apparent that using single wavelength ASE pumping at 1533 nm reduces the fiber length by 10 m (compared to optimized ASE bandwidth pumping) and by 32 m (compared to broadband ASE bandwidth pumping), when L-band EDFA is designed for 25–30 dB signal gain and NF less than 6 dB. These results will be important in designing cascaded wideband EDFA for Optical Fiber Communication (OFC) systems.

Broadband amplified spontaneous emission fibre source near 2 μm using resonant in-band pumping

Broadband amplified spontaneous emission (ASE) at a peak wavelength of 1.85 μm from Tm:Ho-doped silica fibre sources is reported, using in-band pumping from a Yb:Er co-doped fibre laser operating at 1.61 μm. A maximum total output power from both ends of greater than 80 mW with slope efficiency >14% has been achieved. An ASE bandwidth at FWHM of near 70 nm was measured from the forward signal for the output power from 2–40 mW. The total fluorescence spectral width is >200 nm. This broadband ASE source has potential applications in optical metrology, fibre sensors, loss and dispersion tests on optical fibres, spectroscopy and medical imaging, including optical coherence tomography. A review of different pumping schemes in generating ASE around 1.9 μm in the Tm-doped fibre is given. Also the nature of three-level ASE and in-band pumping of Tm:Ho-doped silica fibre are also discussed. The results in this paper confirm that in-band pumped Tm-silica fibre is a route to achieve high power broadband output around 1.8 μm.

Widely tunable S-band fiber-ring lasers and broadband amplified spontaneous emission sources with thulium-doped fluoride fibers

This paper reports our investigation on widely tunable fiber-ring lasers and broadband amplified spontaneous emission (ASE) light sources with thulium-doped fluoride fibers (TDFs). The experimental results for thulium-doped optical fiber amplifiers will also be discussed. We achieved widely tunable fiber lasers that had tuning ranges of 94 nm with 1550 nm + 1050 nm pump configurations and of 85 nm with 1550 nm + 1400 nm pump configurations, respectively. It was observed that the lasers oscillated under multilongitudinal-mode operation with linewidth of 400 MHz, signal-to-source noise ratio of 60 dB, and power stability of 0.003 dB for a laser output of 1 mW. A broadband ASE source with a power density of more than -15 dBm/nm between 1465 and 1535 nm was also demonstrated with a novel hybrid configuration by using both TDF and erbium-doped fiber.

Efficient amplification of a broad-band optical signal through stimulated Kerr scattering in a CS/sub 2/ liquid-core fiber system

Based on the mechanism of stimulated Kerr scattering of anisotropic molecules in a transparent liquid, a broad-band ( approximately 200 AA) ASE (amplified spontaneous emission) signal from a pulsed dye laser amplifier can be significantly amplified by passing through a 2.5 m long CS/sub 2/ liquid-core hollow fiber system. This system is pumped by ultrashort laser pulses with a pulse duration of 4 or 0.5 ps. The measured amplification factor of the ASE signal after passing through the fiber system can be up to 5*10/sup 4/ in the case of 4 ps pump laser pulses, and 4*10/sup 5/ in the case of 0.5 ps pump pulses. The gain saturation and spatially cascaded effect of the stimulated scattering processes become predominant when the pump intensity level is very high (I/sub 0/>or=3 approximately 4 GW/cm/sup 2/).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>