10G DWDM Interconnections Over 120km in Campus Network

With the growing demand for high bandwidth capacity and cost-efficiency, academic and research institutes require Optical Transport Networks to interconnect various buildings, particularly over long distances. One of our clients sought a solution to establish a 10G network between their campus and office, spanning a distance of over 120km, utilizing dark fiber.

In this case, deploying a DWDM infrastructure is the right way for a long-distance transmission with high-quality and reliable network connection. This time FS introduced FMT Series and FMU Series Mux Demux to deal with all of this.

The distance between the campus and the office was 127 kilometers, surpassing the typical range supported by 10G DWDM SFP+ transceivers (commonly up to 100km). We couldn't just use transceiver modules to connect buildings, or signal loss is inevitable. So optical amplifiers and dispersion compensation modules were necessary to amplify signals and fix the deformed signals.

Given the client's lack of expertise in optical networking, FS should guide the client to choose the right products and solutions, as well as in a way that maximized benefits.

Firstly, to achieve long-haul transmission without laying additional fibers, the DWDM Mux/Demux is needed. Mux/Demux gathers all the data streams together to be transported simultaneously over a single fiber. Here, we took dual-fiber Mux/Demux for dual-fiber bidirectional transmission according to the dark fiber that the client can use. 16 channels is a good choice to meet future network expansion and also within the cost budget.

Secondly, we chose Dispersion Compensation Modules according to the link distance. The link distance was 127km, and we only need to compensate for 100km (in practice, the compensation distance will be about 20km less than the actual link distance). We could use 40KM DCM and 60KM DCM to realize compensation and keep the original shape of the signal pulse in long-haul transmission.

Subsequently, the values of the EDFA were verified via the Optical Time Domain Reflectometer (OTDR) report. With a network loss of 26.5dB in the client's report, a minimum link budget of 30dB was necessary to enhance network reliability and account for operational discrepancies. The input power of the pre-amplifier is generally maintained at a minimum of -25dBm, while the booster amplifier's output power should not fall below 5dBm, which is obtained by adding 30dBm to the input power (-25dBm + 30dBm). We calculate the input power for the booster amplifier based on the losses in the link, and then determine the required gain based on this input power value. Finally, we could get the value we need theoretically.

According to the values we had, the technicians recommended the FMT Series for client. The FMT Series can tailor multiple parameters of DCM and EDFA to client's specific needs, such as compensation length, gain values, output/input power connectors, and so on. The client can customize them according to the requirements of the link to achieve the most optimal performance. The right DCM, EDFA and other optical components help amplify the signals and extend your optical infrastructure over 120km.

This solution employed FS FMT and FMU Series, which are known for their cost-effectiveness and stable, efficient connections. With DWDM technology for long-distance transmission, two dark fibers assisted in establishing data connectivity between campus and office buildings over 120km.

Moreover, for novice, the FMU Series Mux/Demux serves as a passive plug-and-play device, requiring no power supply, ensuring convenience and ease of use. The FMT Series features Monitor Online network management software for remote real-time monitoring of network devices and link conditions, thereby reducing the risk of network failures. With FS expert personnel's online guidance and support, the client built a reliable network.