Looking beyond the C-Band

Telecommunications carriers, faced with the challenge of meeting the escalating demand for bandwidth, are looking to Dense Wave Division Multiplexing (DWDM) system providers to help them cost-effectively get more capacity on their fiber optic networks.

To help solve this challenge, DWDM system providers are working on affordable ways to maximize the capacity on existing optical networks. To date, system providers have transmitted data in the C-band – typically operating over 12 to 40 channels.

By utilizing more DWDM channels in the C-band, decreasing channel spacing, and increasing data rates, these providers believe they have a winning strategy in place to meet the growing bandwidth demands that are burdening carriers' networks.

But operating within the boundaries of the C-band may not be enough, as the demand for bandwidth shows no sign of deceleration. The combination of millions of new users on-line, with hundreds of new large bandwidth applications hitting the market every day, is pushing the optical backbone to the limit.

As a result, system developers are realizing they've got to look beyond the C-band as the bandwidth well is sure to run dry—leaving gigabit-thirsty carriers looking for a new watering hole to meet their networks' needs.

Today, major systems manufacturers and carriers are announcing the migration to an entirely new operating band, the L-band (1570 to 1610 nm), with the hopes of doubling overall system capacity.

While L-band expansion taps into as-yet-unutilized bandwidth, it also emphasizes the importance of the system's ability to correct for chromatic dispersion—the natural broadening of light pulses as they travel through optical fiber. Ultimately, dispersion causes pulses to overlap, producing bit errors when optical receivers can no longer differentiate between individual pulses.

The challenge is that dispersion isn't a fixed rate across the operating spectrum. Each channel—or wavelength—disperses at a different rate. The longer wavelengths of the L-band experience more dispersion than the shorter wavelengths of the C-band. This difference in the rate of dispersion across the channels is known as dispersion slope.

So whether they squeeze more out of the existing C-band by adding more channels, or tap into the L-band, carriers have to solve the issue of dispersion slope to take advantage of the bandwidth potential. Their ability to precisely correct for both chromatic dispersion and dispersion slope is critical for the seamless integration and complete utilization of both the C- and L-bands.

At LaserComm, we're making this ability a reality. With trials of our innovative Hi-Mode Dispersion Management Device (DMD) for the C-band already underway with leading DWDM system vendors, we are also well into development of a product for the L-band.

Based on LaserComm's breakthrough higher-order mode technology, the Hi-Mode DMD is the industry's first full slope-matched, broadband solution for chromatic dispersion for all types of non-zero dispersion-shifted fibers (NZDSF).

We will demonstrate both our C-band and L-band version of the Hi-Mode DMD at the Optical Fiber Conference (OFC) held from March 17-22 in Anaheim, CA. Measurements taken throughout the event will demonstrate the Hi-Mode DMD's precise chromatic dispersion and dispersion slope management for all channels across typical spans of NZDSF – the fiber type currently deployed in new advanced long-haul and ultra long-haul optical networks. Please visit us in Hall C, Booth # 1216 to see how LaserComm is enabling carriers to cost-effectively increase capacity in both the C- and L-bands.