Latency equalization for optical filter

A padding unit comprising one or more fiber paddings, wherein each of the one or more fiber paddings is for a respective one of one or more pairs of coupled channels in an optical device, wherein at each pair of coupled channels, one channel in the pair of coupled channels is used as an upstream channel and the other channel in the pair of coupled channels is used as a downstream channel,

• wherein each fiber padding comprises a padding length of fiber configured to offset at least a part of a latency imbalance at the respective pair of coupled channels, wherein the latency imbalance is a difference in latencies between the respective upstream and downstream channels caused by a difference in multiplexing or demultiplexing path lengths of the respective upstream and downstream channels.

A method for manufacturing a padding unit, wherein the padding unit comprises one or more fiber paddings, wherein each of the one or more fiber paddings is for a respective one of one or more pairs of coupled channels in an optical device, and wherein at each pair of coupled channels, one channel in the pair of coupled channels is used as an upstream channel and the other channel in the pair of coupled channels is used as a downstream channel, the method comprising:

• determining a padding length for each of the one or more fiber paddings, wherein the padding length offsets at least a part of a latency imbalance at the respective pair of coupled channels, the latency imbalance being a difference in latencies between the respective upstream and downstream channels caused by a difference in the multiplexing or demultiplexing path lengths of the respective upstream and downstream channels;
• and
• forming the one or more fiber paddings based on the one or more determined padding lengths.