Marc Mermelstein

SBS threshold measurements and acoustic beam propagation modeling in guiding and anti-guiding single mode optical fibers

A 4.3 dB stimulated Brillouin scattering (SBS) threshold suppression is measured in a passive Al-doped acoustically anti-guiding single mode optical fiber relative to that of a Ge-doped acoustically guiding single mode optical fiber. Stimulated scattering is generated by the electrostrictive acoustic wave generated in the fiber core. This acoustic excitation has a decay length L(d) related to the sound absorption decay length L(abs) and the acoustic waveguide decay length L(wg) by: L(d)(-1)= L(abs)(-1)+ L(wg)(-1). The acoustic waveguide decay length L(wg) is associated with the diffraction, refraction and reflection of the acoustic wave in the elastically inhomogeneous optical fiber cores. The SBS gain is proportional to the net acoustic decay length L(d) and the relative SBS suppression is proportional to the ratio of the net decay lengths of the Al and Ge doped cores (L(Al)/ L(Ge)). An acoustic beam propagation model is used to calculate the evolution of the complex acoustic excitations in the optical cores and determine the acoustic wave decay lengths L(wg). Model predictions for the relative SBS suppression for the two fibers are in good agreement with experimental values obtained from Stokes power and optical heterodyne linewidth measurements.

SBS gain efficiency measurements and modeling in a 1714 µm 2 effective area LP 08 higher-order mode optical fiber

The stimulated Brillouin scattering (SBS) gain efficiencies were measured in the LP(08) and LP(01) modes of a higher-order-mode optical fiber. Gain efficiencies C(B) of 0.0085 and 0.20 (m-W)(-1) were measured for the LP(08) and LP(01) modes at 1083 nm, respectively. C(B) is inversely proportional to the optical effective area Aeff and the same core-localized acoustic phonon seeds the SBS process in each case. An acoustic modal analysis and a distributed phenomenological model are presented to facilitate the data analysis and interpretation. The LP(08) mode exhibits a threshold powerlength product of 2.5 kW-m.

Modeling of inter-modal Brillouin gain in higher-order-mode fibers.

Finite element calculations of inter-modal Brillouin gain between LP(0n) modes in acoustically-inhomogeneous higher order mode (HOM) fibers are presented. When the pump beam is launched in the LP(08) mode, the LP(01) mode of the Stokes beam experiences the highest gain, approximately 6.7 dB higher than the peak LP(08)-LP(08) gain. An LP(01) Stokes beam experiences successively more Brillouin gain when pumped by higher-order LP(0n) modes.

Configurability of a three-wavelength Raman fiber laser for gain ripple minimization and power partitioning

The performance of a 3/spl lambda/RFL with variable OC reflectivities was investigated in 60 km, 100 km and 140 km transmission spans. The data indicates that this device is practical and can provide stable broadband optical amplification. A gain ripple minimum of 1.1 dB in a 100 km span, in agreement with simulations, is achieved with an OC voltage precision of 25 mV. The gain ripple /spl Delta/G and power partition deviation /spl Delta//spl rho/ voltage sensitivities were found to be /spl sim/0.01 dB/mV and /spl sim/0.04%/mV, respectively. This low sensitivity means control of the output powers of a multi wavelength RFL is not considerably more complicated than controlling multiplexed individual lasers.

Raman fiber lasers as pumps for Raman amplification

This article describes Raman fiber lasers and their application as pumps to a Raman amplified optical communication system. Single wavelength, multiwavelength and dual-order devices are described. The advantages of Raman fiber lasers compared to semiconductor diodes are also discussed.

Yb-doped amplifier fiber with distributed filtering by resonant core-ring coupling

An Yb-doped amplifier fiber with distributed gain filtering along its length was fabricated. Measured amplified spontaneous emission confirms gain suppression at wavelengths relevant to important laser noise components. Pump efficiency improvement was observed.

Six wavelength Raman fiber laser for C + L-band Raman amplification

Summary form only given. Reported here is the first six-wavelength Raman fiber laser whose power distribution can be controlled to provide broadband adjustable gain in the C and L telecommunications bands. Radiation at 1100 nm is injected into a cascaded Raman resonator (CRR) where successive Raman shifts generate radiation at 1347 nm. The radiation at 1347 nm is coupled to resonant cavities at the six lasing wavelengths; 1428, 1445, 1466, 1480, 1494 and 1508 nm. The resonant cavities are constructed with six broadband high reflectivity (/spl sim/99%) Bragg gratings and six adjustable-reflectivity voltage-controlled output couplers. Stokes radiation at 1347 nm provides Raman gain for lasing at all six cavity resonances. The shorter wavelength radiation provides additional gain to the longer wavelength spectral components. Hence, the spectral power distribution is dependent upon the power in any individual spectral component.

Suppression of stimulated Raman scattering in a cladding pumped amplifier with an Yb-doped filter fiber

A cladding-pumped, high-power amplifier was built incorporating a star-shaped, Ybdoped filter fiber. Pulsed amplifier measurements demonstrate strong suppression of stimulated Raman scattering accomplished by a special index profile with an up-doped ring.

Accurate measurement of pulse power in low duty cycle MOPA

There can be a significant amount of interpulse signal present in low-duty cycle MOPA. This requires that both spectral and temporal filtering be used to accurately determine signal power within the pulse width.

RIN transfer suppression technique for 2nd order Raman pumping schemes

An optical technique is demonstrated for suppressing the relative intensity noise (RIN) transfer from a high-power second-order pump laser to the signal radiation in a copropagating dual-order Raman pumping scheme. RIN transfer suppression is accomplished by intensity-modulating a low-power semiconductor laser diode first-order pump. Measurements are presented demonstrating suppression over the entire electronic bandwidth and -20-dB suppression spanning a 23-nm optical bandwidth. This technique may facilitate the use of high-power fiber lasers in copropagating dual-order distributed Raman amplifiers.RIN transfer suppression in 2nd order co-propagating pumping schemes is demonstrated. Suppression is achieved by intensity-modulating the seed laser. This technique may enable the use of Raman fiber lasers in co-pumping architectures. An optical technique is demonstrated for suppressing the RIN transfer from a high power lower order pump to the signal radiation in a co-propagating 2nd order pumping configuration. RIN suppression is accomplished by intensity-modulating the intermediate wavelength seed semiconductor laser diode.