Long-haul DWDM Transmission With Optical Line Protection


DWDM network helps maximize the use of existing fiber and optimize the network investment. Our client, a leading solution provider for Internet, networking and cable TV in Europe decided to expand the capacities of their optical transmission link over 79km and planned for a 120km backup path for future scalability.


The client needed to improve their network infrastructure and desired to build a more reliable and scalable network. The problems they encountered including:

  • How to establish link protection while achieving future capacity expansion?

  • How to reduce optical loss and ensure enough reserve budget for reliable and stable transmission over long distance transmission?


FS engineers planned to deploy a 40CH DWDM system with optical line protection to feed the customer’s current and future growth demands for networking capacities.

The OEOs are used to convert the 1G and 10G optical signals into the corresponding DWDM wavelengths. And 1+1 optical line protection switch (OLP) is deployed to create a backup path. When the main optical fiber fails, the protective line will continue to deliver the signal. Therefore, the whole transmission will be more reliable.

To reduce the optical loss on the primary path, the booster amplifier (OBA) is used to increase the power of the transmitted light. The pre-amplifier (OPA) is applied for amplifying the weak optical signal. In addition, several optical attenuators are used to ensure the optical power in a stable and desired level. In this solution, the optical loss on primary link could be 21dB and there will be 5dB for reserve budget, while the optical loss of backup path could be 34dB, with 4dB reserve budget.

Long-haul DWDM Transmission


FS 40CH DWDM solution not only feeds the current transmission need, but also prepares well for future expansions. And with OLPs on both sides, the signal can be boosted and protected across the whole link, which improves network stability.

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