measure transceiver wavelength

m4rtin

In case there is an optical transceiver(for example SFP, GBIC or XFP) which has no label on it and EEPROM data is damaged, is there a method to measure Tx wavelength? In case of 1000BASE-SX transceivers one might see the red light because light source output often includes some alien wavelengths around the 850nm and human eye is able to detect from 700nm, but what about higher wavelengths? Or is the only method to use optical spectrum analyzer?