M.E. Marhic

BROADBAND FIBER OPTICAL PARAMETRIC AMPLIFIERS

The bandwidth of a single-pump fiber optical parametric amplifier is governed by the even orders of fiber dispersion at the pump wavelength. The amplifier can exhibit gain over a wide wavelength range when operated near the fibers zero-dispersion wavelength. It can also be used for broadband wavelength conversion,with gain. We have experimentally obtained gain of 10-18 dB as the signal wavelength was tuned over a 35-nm bandwidth near 1560 nm.

Wide-band tuning of the gain spectra of one-pump fiber optical parametric amplifiers

By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra. These can range from a very wide single region to two symmetric narrow gain regions far away from the pump. We have experimentally verified these predictions. With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB. With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0/spl deg/C.

Polarization-independent two-pump fiber optical parametric amplifier

Fiber-optical parametric amplifiers can be rendered polarization-independent by using two pumps with orthogonal polarization states. We have analytically investigated and experimentally demonstrated, for the first time to our knowledge, a flat-gain polarization-independent continuous-wave fiber optical parametric amplifier with 15 dB of gain over a 20-nm bandwidth, by using two orthogonal pumps.

Broadband fiber-optical parametric amplifiers and wavelength converters with low-ripple Chebyshev gain spectra

We have shown that the propagation constant mismatch /spl Lambda//spl beta/ for a 2-pump fiber OPA can be well approximated by a fourth-order Chebyshev polynomial, by adjusting /spl omega//sub c/, near /spl omega//sub 0/, and the pump spacing. Very low gain ripple can be obtained over tens of nanometer. This level of performance is not available with any other type of optical amplifier. It could make fiber OPAs and related wavelength converters attractive when multiple stages are required.

Coherent optical CDMA networks

Recent work in optical code-division multiple access (CDMA) is reviewed, progressing from incoherent to coherent techniques. It is shown that under appropriate conditions, coherent CDMA can in principle rival wavelength-division multiplexing (WDM) in terms of aggregate network throughput. Furthermore, it is shown that at high data rates, some of the components for WDM are coherent CDMA networks are nearly identical, indicating a similarity between the two approaches. CDMA retains a coding aspect which may prove attractive in security applications. >

Polarization-independent one-pump fiber-optical parametric amplifier

One-pump fiber optical parametric amplifiers (OPAs) can be rendered polarization independent by using a polarization-diversity technique. We have experimentally demonstrated a fiber OPA with peak signal gain of 9 /spl plusmn/ 0.2 dB when the signal polarization angle was varied from 0/spl deg/ to 90/spl deg/. Power penalty of less than 1 dB was measured in a 10-Gb/s transmission system.

Discrete Fourier transforms by single-mode star networks.

A single-mode star network, made from polarization-preserving components, can perform the spatial discrete Fourier transform of coherent light patterns presented at the inputs. This can be accomplished with passive components, such as 2 x 2 couplers, and propagation delays. The Hadamard transform can be performed similarly.

High-nonlinearity fiber optical parametric amplifier with periodic dispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength /spl lambda//sub p/ far from the fiber zero-dispersion wavelength /spl lambda//sub 0/ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for /spl lambda//sub p/=1542 and /spl lambda//sub 0/=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber.

Continuous-wave fiber optical parametric wavelength converter with +40-dB conversion efficiency and a 3.8-dB noise figure

We have obtained 40 dB of internal (on-off) conversion gain and a sub-4-dB noise figure (NF) with a continuous-wave (cw) fiber optical parametric wavelength converter. To our knowledge, this is the lowest NF reported for any cw wavelength converter. We have also investigated the properties of NF versus signal input power and pump power.

Low‐order TE0q operation of a CO2 laser for transmission through circular metallic waveguides

We report the separate TE01 and TE02 operation of a CO2 laser in a hybrid oscillator formed by placing a circular metallic waveguide and a focusing lens inside the cavity of an otherwise conventional laser. With the TE01 output focused into a passive waveguide outside the cavity, transmission in excess of 90% has been measured through a 31‐cm‐long, 0.5‐mm‐i.d. straight metallic tube. Bending increased the losses far more than originally anticipated.