Photonetics 3651 HR 12 Optical Spectrum AnalyzerPhotonetics 3651 HR 12 Optical Spectrum Analyzer (OSA) The unit shows "self reference error" message. However, it can be by passed easily. You can set a wavelength offset to do manual calibration when needed. Once calibrated, the unit works repeatedly and reliably. Once the offset is set up, you just ignore the error message when turning on the unit. It will not change during switching on and off. This unit is to be sold "AS IS". No return and no