Measurement of spectra of fiber Bragg gratings by tuning the wavelength of a laser diode

•Spectra of fiber Bragg gratings can be measured by tuning off-the-shelf laser diode.•Resolution of 2 pm has been achieved in the spectra measured by tuning.•Current tuning enables interrogation of fiber gratings at frequencies up to 100 kHz.•Shift of fiber Bragg grating spectra upon heating can be measured by laser diode.