Aspects of the present disclosure describe distributed fiber optic sensing systems (DFOSa), methods, and structures for distributed temperature sensing (DTS) that 1) employs a GmAPD instead of a traditional LmAPD detector which advantageously produces a 10˜20 dB gain improvement of SNR for a far-end weak signal, thereby improving long range detectability; 2) employs an inventive gating scheme that advantageously and surprisingly overcomes the “dead time” problem for GmAPD working in SPC mode that plagues Geiger mode operation; and 3) third, employs an inventive post-processing technique that advantageously allows our methods to correct any dark noise caused signal distortion.