Do you have Optical line protection solution? For 20km, The loss 15dB max. Yes, The following is reference solution diagram from HTF for you reference. HTF OLP1+1 Solution Item Model Specification Site A Quantity (pcs) Site B Quantity (pcs) Sub total A+B Quantity (pcs) 1U Chassis HT6000-CH04 1U, 19-inch, 3 universal service slots, 1 network… Continue reading OLP 1+1 Optical Line Protection Solution