Data Denters with Channel Redundancy

Technical task

Connect two sites located at a distance of ~30 km from each other.?Providing fiber redundancy is a prerequisite for the TOR, that is, the operation of communication channels should not be disrupted even in the event of a break in one of the fibers.?The total capacity between the two sites should be 2 x 40GE links on the QSFP+ client ports and one FC16G link on the SFP+ client port of the SAN switch.

Initial data

Between the sites, the Customer rents 2 optical fibers in cables laid along different routes.

Decision

A certain complexity of the project lies in the fact that it is not possible to organize the transmission of a channel from QSFP+ transceivers in one fiber, since such a form factor simply does not exist in a single-fiber version.?As for DWDM QSFP+, the mention of the modules can be found on the Internet, but they are not available for wide commercial use, and they also have low stability.

A simple, but at the same time expensive solution to this problem is the use of an aggregating muxponder, which allows you to combine 2 QSFP and 1 SFP+ into a 100G OTN channel.

We offered the Customer an alternative option that provides reasonable cost savings, namely the use of QSFP+ DAC cables in 4 x SFP+ in the Breakout system.?Received 10G channels are converted to DWDM SFP+ using OEO interface converters, compressed into a group signal and transmitted in one fiber.?The ability to use DWDM SFP+ FC16G transceivers in a SAN switch allows you to easily organize the transmission of FC16G with Ethernet channels.

During the development process, the specific features of the project were also taken into account (with redundant channels through optics).?The primary fiber redundancy device is the optical switch.?However, the use of this equipment leads to additional attenuation in optical fibers, and depending on the principle of operation of the switch (1 + 1 or 1: 1), the attenuation will be different.

Separately, it should be noted that the standard scheme for using OLP switches assumes the presence of four fibers, and in our case there are only two.?In this regard, we introduced R / B filters into the circuit and additionally took into account the attenuation on them.?The recalculation of the total attenuation showed that the value of the optical budget exceeded the allowable limit, so optical amplifiers were added to the final circuit.