Min-Chen Ho

200-nm-bandwidth fiber optical amplifier combining parametric and Raman gain

Theory shows that the gain bandwidth of a one-pump fiber optical parametric amplifier (OPA) using highly nonlinear fiber (HNLF) could be more than 200 nm. Under these circumstances, the OPA gain would overlap the pump-induced Raman gain. We have studied the combined effects of OPA and Raman gain theoretically and experimentally. The experimental results demonstrate a 200-nm bandwidth from a single fiber-optical amplifier and also verify that the influence of the Raman effect is relatively small, as predicted by the theory.

Narrow-linewidth idler generation in fiber four-wave mixing and parametric amplification by dithering two pumps in opposition of phase

Wide-bandwidth and high-gain fiber optical parametric amplifiers (OPAs) have been demonstrated recently. Their application as all-optical wavelength converters has been hampered by pump-induced converted-signal spectrum broadening, due to the required pump phase modulation. In this paper, we theoretically investigate and experimentally demonstrate a technique to cancel the converted-signal broadening by using four-wave mixing (FWM) or parametric amplification with two pumps phase-modulated 180/spl deg/ out of phase. The resulting converted-signal quality is comparable to that of the output signal.

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.

92% pump depletion in a continuous-wave one-pump fiber optical parametric amplifier.

Theory shows that near-complete pump depletion can be obtained in uniform fiber-optic parametric amplifiers (OPAs) for a particular phase-matching condition. We have demonstrated 92% pump depletion in a cw fiber OPA, with a 200-mW pump at 1560 nm in an 11-km-long dispersion-shifted fiber.

Distributed slot synchronization (DSS): a network-wide slot synchronization technique for packet-switched optical networks

Distributed slot synchronization (DSS) is a network-wide packet synchronization technique which coordinates node transmissions so that packets arrive aligned to one another at a reference point in the network, independent of propagation delays. DSS was developed for use in the contention resolution with delay-lines (CORD) project, a DARPA-funded 2.5 Gb/s//spl lambda/, wavelength division multiplexer (WDM) optical packet-switched network testbed. In this implementation, it was experimentally demonstrated that the DSS system, operating with 80 MHz control logic, achieves a packet arrival jitter of less than 13 ns with 12 km node spacings. DSS was also shown to be robust against noise and node failure or fiber breaks. The technique is data rate and format independent and can be used in other star, extended ring, or tree-and-branch network architectures for metropolitan area network (MAN) and access applications.

Fiber optical parametric amplifier and wavelength converter with 208-nm gain bandwidth

Summary form only given. Recently, we demonstrated a fiber OPA with 120-nm bandwidth, limited by our measurement capabilities. We report measurements with an improved measurement system, and demonstrate a fiber OPA with a 208-nm bandwidth. To our knowledge, this sets a new record for the bandwidth of fiber amplifiers, of any kind. The role of Raman amplification is quantitatively taken into account.

35-dB nonlinear crosstalk suppression in a WDM analog fiber system by complementary modulation of twin carriers

We investigate, theoretically and experimentally, a novel scheme to suppress the crosstalk between wavelengths in wavelength-division-multiplexing (WDM) analog fiber systems. The idea is based on the fact that crosstalk (due to stimulated Raman scattering and cross-phase modulation combined with group velocity dispersion), is caused by the intensity modulation of one channel affecting a second channel in a WDM system. Then, if an auxiliary carrier (twin) with complementary modulation is introduced very close to the first channel, their combined intensity will be constant and there will be no nonlinear crosstalk induced at the second channel. We have obtained up to 35-dB crosstalk reduction at low modulation frequencies, where crosstalk is most severe.

Idler spectral broadening suppression in two-pump fiber optical parametric amplifier

We have demonstrated the suppression of idler broadening in a two-pump fiber optical parametric amplifier by dithering the two pumps with out-of-phase signals. Idler spectrum linewidth almost the same as signal linewidth is observed.

Optical parametric amplification in a high-nonlinearity fiber

We have demonstrated a fiber optical parametric amplifier (OPA) utilizing a highly nonlinear fiber, which allowed us to obtain substantial gain with only a 20-m length, over a 24-nm bandwidth, even though the pump was 49 nm from /spl lambda//sub 0/. The availability of such fibers should greatly facilitate the development of fiber OPAs for applications such as wavelength conversion, phase conjugation, and broadband amplification.

Nonlinear cross-talk reduction by spectrum shaping in subcarrier signaling WDM networks

A key issue in developing WDM networks is how to implement the control channel for medium access control and network reconfiguration. The SCM signaling modulates the control channel at a microwave subcarrier and multiplexes with the high-speed payload data at base band, which provides a high-performance and low-cost solution for the signaling implementation in WDM networks. A major performance limitation of SCM signaling comes from various nonlinearities. These nonlinearities generate cross talk proportional to the product of base-band data and the subcarrier in the time domain. In the frequency domain, the cross talk appears as a (two-sided) replica of the base-band spectrum upconverted at the subcarrier frequency because of the spectrum convolution. Because the cross-talk spectrum is an upconverted data spectrum, if we shape the data spectrum to place a null at DC, the cross-talk spectrum will reproduce a null at the subcarrier frequency. Because the subcarrier is a narrow-band signal, the null centered at the subcarrier frequency suppresses the cross-talk penalty significantly. Several line-coding techniques can generate a DC-null spectrum. We focused on Manchester coding because of its simplicity and advantages in clock recovery and burst-mode data receiving.