| 摘要 |
A system, circuit and method are disclosed for operating an RLG off-mode-peak to avoid exciting undesirable transverse modes. An alternate PLC operating point can be used to bias the optical path length of the RLG to an appropriate side of an ideal integer number of wavelengths, and thus avoid exciting the undesirable transverse modes. Although this alternate PLC operating point is not perfect with respect to establishing an integer number of wavelengths, this operation provides acceptable performance of the RLG's (in particular, short length path RLG's), and acceptable margin can be established relative to variations in the PLC set points involved. For example, a PLC loop can be used to dither about this operating point as a discriminate to allow closed loop control of the path length. Also, a PSSD control architecture can be used to establish and maintain a requisite path length over relatively wide variations in operating temperature. Specifically, a small offset error can be injected into a conventional PSSD loop for an RLG, which causes the loop to converge on a pre-selected operating point that is on one side of a conventional convergence point. The magnitude and polarity characteristics of this operating point offset can be determined for each RLG, or such characteristics can be consistently used for a family of RLG's.
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