G. Nykolak

Optimal dispersion of optical filters for WDM systems

The phase response of optical filters determines their dispersive properties and impacts wavelength-division multiplexing (WDM) system performance. We present a general analysis of the phase response of optical filters used in WDM systems and suggest ways to minimize the detrimental dispersive effects of these filters. Some filters are found to be inherently linear phase filters and in principle are dispersionless. We also show that some filters may be realized for the phase correction of dispersive filters. Experimental system results demonstrate the negative effects of filter dispersion on system performance.

Concentration-dependent /sup 4/I/sub 13/2/ lifetimes in Er/sup 3+/-doped fibers and Er/sup 3+/-doped planar waveguides

We report on the concentration- and pump-dependent lifetimes of the spontaneous emission in Er/sup 3+/-doped fibers and Er/sup 3+/-doped waveguides. In addition, we measure the concentration dependence of the 550-nm fluorescence due to excited state absorption (ESA).<<ETX>>

8-mV threshold Er/sup 3+/-doped planar waveguide amplifier

We report on the gain characteristics of a low threshold (8 mW) Er/sup 3+/-doped planar optical waveguide amplifier. Net fiber to fiber gain of 4.5 dB is achieved at a signal wavelength of 1536 nm with 80 mW of 980-nm pump power. This device represents significant progress toward a planar amplifier module pumped by a single laser diode.

Systems evaluation of an Er/sup 3+/-doped planar waveguide amplifier

We report the output saturation power, excess noise factor, and system performance of a highly concentrated Er/sup 3+/-doped planar optical waveguide amplifier. The performance data demonstrate the potential usefulness of planar optical waveguide amplifiers in system applications.<<ETX>>

Dispersion penalty measurements of narrow fiber Bragg gratings at 10 Gb/s

We measure the dispersion penalty of a narrow fiber Bragg grating (0.25 nm) at 10 Gb/s, in both transmission (pass through channel) and reflection (drop channel). We investigate the effects of transmitter chirp conditions on the dispersion penalty performance.

An erbium-doped multimode optical fiber amplifier

The authors describe the first experimental study of an erbium-doped multimode fiber amplifier. The focus has been to characterize an intermediate core erbium-doped optical fiber, a fiber that is capable of propagating many guided modes at both the signal and pump wavelengths, and to determine the feasibility of using such an active fiber as a multimode fiber amplifier, by measuring its gain, noise, and pump power requirements. For a 2-m length of a 13- mu m-core erbium-doped fiber, the authors measured gain as high as 16 dB at a signal wavelength of 1543 nm, with approximately 100 mW pump power (980 nm). For these same test conditions, the smallest excess noise factor beta was 42.<<ETX>>

Photoluminescence and electrical properties of erbium‐doped indium oxide films prepared by rf sputtering

Erbium‐doped indium oxide films were prepared by rf magnetron sputtering. The Er‐doped oxide films are conducting (or semiconducting) with a resistivity in the range of 10−3–103 Ω cm, and are optically active, i.e., show a clear room‐temperature photoluminescence at 1.54 μm, corresponding to intratransitions in Er3+ ions. Compared with the undoped indium oxide films, the erbium doping was found to have the effect of increasing the resistivity (up to two orders of magnitude) of the films, mainly via a reduction of carrier concentration. Postdeposition annealing in air ambient significantly enhances both the Er3+ luminescence and Hall mobility (up to 60 cm2/V s), and reduces the carrier concentration. Postdeposition annealing in reducing ambient (N2/H2), however, decreases the resistivity dramatically, mainly via an increase of carrier concentration (up to 1020 cm−3), and also enhances the Er3+ luminescence.

4/spl times/2.5 Gb/s 4.4 km WDM free-space optical link at 1550 nm

We describe a new worlds record for free-space optical communications realized with a 4-channel, 2.5 Gb/s per channel system, operating error-free over a free-space horizontal distance of 4.4 km. This is made possible by three key developments: (1) specialized optical telescope-transceiver terminals, (2) multimode fiber DWDMs and (3) high power 1550 nm Er/Yb optical amplifiers.

160-Gb/s free-space transmission link

12 We demonstrate record error-free transmission of a single 160 Gb/s RZ data channel at 1550 nm over 200 meters of free space. This represents the largest data bandwidth transmitted over this distance, without the use of optical fibers.

Impact of fiber grating dispersion on WDM system performance

Summary form only given. Fiber gratings have become one of the important optical filtering devices in wavelength-division multiplexed (WDM) communication systems. These filters are inherently dispersive elements, which affect the pulses propagating through or reflecting off them by spreading them in time. This dispersion-induced pulse broadening leads ultimately to transmission penalties. Recently the effect of fiber grating dispersion on neighboring transmitted channels was analyzed and it was found that the increasing dispersion near the grating band edge leads to unacceptable pulse broadening and therefore to a lower limit on channel spacing for a given bandwidth of modulation. In this paper, we present the results of a system experiment in which both the transmission and reflection are investigated. 10 Gbit/s system measurements confirm the detrimental effects of fiber grating dispersion close to the band edges. These dispersion effects may ultimately impose limits on the channel bandwidth to channel spacing ratio (spectral utilization).