Table 1.

Time delays and optical fiber lengths for PADLs.

Fiber number	Signal arrival (μs)	1st Echo arrival (μs)	Fiber length (mm)
1	44	132	225
2	56	168	286
3	68	204	347
4	80	240	409
5	92	276	470
6	104	312	531
7	116	348	593
8	128	384	654

The incremental time delay between fibers is 12 μs, and the acoustic velocity in silica optical fibers is $\sim 5108\mathrm{m}/\mathrm{s}$.