Justin B. Judkins

Long-period fiber gratings as band-rejection filters

We present a new class of long-period fiber gratings that can be used as in-fiber, low-loss, band-rejection filters. Photoinduced periodic structures written in the core of standard communication-grade fibers couple light from the fundamental guided mode to forward propagating cladding modes and act as spectrally selective loss elements with insertion losses act as backreflections <-80 dB, polarization-mode-dispersions <0.01 ps and polarization-dependent-losses <0.02 dB.

Long-period fiber-grating-based gain equalizers

Long-period fiber gratings are used to f latten the gain spectrum of erbium-doped fiber amplifiers. A broadband amplifier with <0.2-dB gain variation over 30 nm is presented. We also show that a chain of amplifiers can be equalized, leading to a bandwidth enhancement by a factor of 3.

Broad-band erbium-doped fiber amplifier flattened beyond 40 nm using long-period grating filter

Broad-bandwidth amplification is essential for the construction of high-capacity multichannel communication systems. We describe a silica-based erbium doped fiber amplifier (EDFA) with a flat gain bandwidth exceeding 40 nm. The dual-stage EDFA includes a precisely designed inter-stage long-period fiber grating filter with more than 14-dB peak attenuation. By careful choice of the filter spectrum and fiber lengths, this EDFA is flat to within 1 dB over 40 nm while producing a noise figure below 4.0 dB and nearly +15-dBm output power.

A gain-flattened ultra wide band EDFA for high capacity WDM optical communications systems

An 84 nm gain-flattened ultra wide band erbium-doped silica fiber amplifier for high capacity WDM optical communication systems is demonstrated with a noise figure of 6 dB and an output power of 25 dBm. We demonstrated an ultra wide band EDFA with a two-section, split band structure. The total 3dB bandwidth is 84.3 nm, which should be able to support 100 WDM channels with 100 GHz channel spacing or 200 WDM channels with 50 GHz channel spacing. The split bands allow independent optimization of each band for dispersion compensation and span loss variations.

Transmission of 32-WDM 10-Gb/s channels over 640 km using broad-band, gain-flattened erbium-doped silica fiber amplifiers

We report 640-km transmission of 32 wavelength-division-multiplexed (WDM) 10-Gb/s channels with 100-GHz spacing (covering 25-nm bandwidth) using wide dynamic range, gain-flattened erbium-doped silica fiber amplifiers (EDSFAs) with an optical bandwidth of 35 nm. The EDSFA separation is 80 km, the system gain is 140 dB and the total end of system gain nonuniformity among the 32 channels is 4.9 dB.

Ultra Wide Band Erbium-Doped Silica Fiber Amplifier with 80 nm of Bandwidth

The design of wavelength-division-multiplexed (WDM) systems and optical networks is currently constrained by the limited bandwidth available from erbium-doped fiber amplifiers (EDFAs) because of their nonuniform gain spectra.

Error free transmission of 64 WDM 10 Gb/s channels over 520 km of Truewave/sup TM/ fiber

We report error-free transmission of 64/spl times/10 Gb/s channels with 50 GHz spacing using high power, flat gain (35 nm bandwidth) erbium-doped silica fiber amplifiers. The amplifier spacing was 80-40 km, and the total end-of-system gain nonuniformity among the 64 channels was 6.4 dB.

Reliability of long-period gratings

Summary form only given. Ever since their conception in 1996, long-period gratings (LPGs) have come to be used in a wide variety of applications. LPGs involve coupling of core and cladding modes. The importance of thermal stabilization techniques for successful use of Bragg gratings is now well acknowledged. This is even more important in LPGs, because the wavelength at which the coupling from the core to the cladding modes takes place is directly dependent on the UV-induced refractive-index change (/spl Delta/n/sub UV/) and on n/sub core/-n/sub clad/ (/spl Delta/n). A decrease in these can greatly shift the spectra in a LPG. For example, thermal conditions that cause a 2% decrease in n/sub UV/ would have a negligible effect in a add/drop wavelength-division multiplexed (WDM) Bragg grating (/spl Delta//spl lambda/<10 picometers) but a similar decay in the case of a LPG would shift its center wavelength by about 0.5 nm, which is unacceptable for most applications (such as gain equalizers). In this paper, we present a method to analyze and predict LPG decay. Using our analysis method we have arrived at stabilization conditions yielding LPGs with predicted end-of-life (25 years) shifts of <0.02 nm at 40/spl deg/C and <0.12 nm at high aggressive conditions (60/spl deg/C).