Maintaining quality of packet traffic in optical network when a failure of an optical link occurs

A method of protecting packet traffic against failures in an optical network comprising routers, optical fibers, and optical switches interconnecting routers and optical fibers, comprising the steps of:

• arranging 1+1 protection comprising two optical links in separate optical fibers for traffic of high priority packets between a transmitting router and the corresponding receiving router;
• routing at the transmitting router packets of high priority to both of the optical links, wherein after a fiber cut in either of the optical links occurs the corresponding receiving router continues reception of the packets form the remaining optical link without noticeable delay;
• and
• arranging 1:1 protection comprising at least the first and the second optical link in separate optical fibers for traffic of middle and low priority packets between a transmitting router and the corresponding receiving router;
• routing at the transmitting router packets of middle priority to the first optical link,
• routing at the transmitting router packets of low priority to the second optical link, and
• in response to a fiber cut in the first optical link, rerouting at the transmitting router the packets of middle priority to the second optical link and rerouting the packets of low priority to the first optical link, whereupon at the corresponding receiving router reception of the middle priority packets continues after a short switching delay but the low priority packets are lost;
• in response to a fiber cut in the second optical link, retaining routing at the transmitting router, whereupon at the corresponding receiving router reception of the middle priority packets continues without delay but the low priority packets are lost.