A 1320 nm Experimental Optical Phase-Locked Loop

Bellcore, Red Bank, NJ, USA
IEEE Photonics Technology Letters (Impact Factor: 2.11). 12/1989; 1(11):395 - 397. DOI: 10.1109/68.43391
Source: IEEE Xplore


An experimental balanced optical second-order phase-locked loop constructed using 1320 nm diode laser pumped miniature Nd:YAG lasers is discussed. The loop is stable and has a phase error of less than 1.8 degrees when the received signal power is -65 dBm or more. The phase error appears to be dominated by the lasers' frequency noise as long as the signal power is more than -60 dBm.< >

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    • "Although simple in principle and demonstrated for narrow-linewidth gas lasers at an early stage in laser development [43], the practical realization of OPPLs is limited by the requirement that the loop delay should be small enough to ensure that phase fluctuations of the optical sources are accurately cancelled [44], [45]. The requirement for subnanosecond loop delays to lock nonline narrowed semiconductor lasers led to much early work being carried out with narrow-linewidth solid-state [46], [47] or external cavity semiconductor [48] lasers. Nevertheless, by careful microoptical design , first homodyne [49] and, subsequently, heterodyne [50], [51] loops were successfully realized using nonline narrowed semiconductor lasers with linewidths of an order of 10 MHz, yielding reference source limited phase noise of better than 83 dBc/Hz at offsets of a few megahertz, as shown in Fig. 4. "
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