為降低保護切換代價和提高故障恢復時間，提出了以光纖級P-Cycle來實現網絡保護；研究了工作路由與光纖級P-Cycle放置聯合優化的設計問題，給出了ILP數學模型。為降低計算的復雜度，采用了一種簡單有效的方法：根據跳數預先選擇工作路由候選集及環的有效性和長度預先選擇P-Cycle候選集。仿真結果表明光纖級P-Cycle設計相比于波長級P-Cycle設計保護切換代價大大降低。

To reduce the protection-switching cost and failure recovery time, the fiber-level P-Cycles is presented to realize network protection. The issue about the joint optimization design of the working path routes with fiber-level P-Cycle placement is further studied; and an improved ILP formulation is developed. To reduce the complexity of joint optimization problem, the simple process of pre-selecting candidate P-Cycles by the efficiency and length metric and candidate working path routes by the hop metric is used. By simulation analysis, the fiber-level P-Cycles scheme efficiently decreases the switching cost compared with the wavelength-level P-Cycles.