Brillouin analysis with 8.8 km range and 2 cm resolution

Brillouin analysis of a 8.8 km-long fiber with 2 cm resolution is reported. Pump and signal are jointly modulated by a binary phase Golomb code. Over 2,000 correlation peaks are simultaneously introduced and interrogated in a single trace. All 440,000 resolution points are covered in just 211 scans of peaks positions. The pump wave is amplitude modulated by a second, 10,000 bits long code. Post-processing of the output signal provides a measurement signal-tonoise ratio that is equivalent to that of 5,000 single-pulse acquisitions. A 7cm-long hot spot is identified. The uncertainty in Brillouin frequency measurements is +/- 3.5 MHz.