クロック回復なしのデータ回復

摘要

If clock frequency difference between a transmitter and a receiver is small, data recovery without clock recovery is possible if received signal is passed through a variable delay line and phase of the signal is synchronized to receiver's clock using DLL (Delay Locked Loop), as long as phase difference between the signal and receiver's clock is within variation range of the variable delay line. This method is useful for packet communication as time to retain phase synchronization is short and is especially useful for many wavelength packets as each wavelength contains small number of bits to which quick phase synchronization is necessary. Similarly, optical analog coherent reception is possible, if frequency difference between LOs (Local Oscillators) of a transmitter and a receiver is small and received light is passed through a variable delay line and phase of the light is synchronized to receiver's LO.%送信側と受信側のクロック周波数の差が小さければ，受信信号を可変遅延線に通しDLLで受信側クロックに位相同期させることで，受信信号と受信側クロックの位相のずれが可変遅延線の可変範囲の間，クロック回復なしのデータ回復が行える.この方式は位相同期維持時間が短いパケット通信に有効で，特に，各波長に含まれるビット数が少なく迅速なクロック同期が必要な多波長パケットに有効である.同様に，送信側と受信側のLOの周波数の差が小さければ，受信光を可変遅延線に通しDLLで受信側LOに位相同期させることで，アナログコヒーレント受光も行える.