Table 9 Advantages and characteristics of different schemes for simultaneous improvement of sensing distance and spatial resolution

Pulse modulation based on single-mode fiber

It can ensure a better spatial resolution along with extension of the sensing distance.

(1) An extra expense (EOM and coding generator) and operational complexity for practical application.

(2) The theorical spatial resolution is limited to the pulse width, which is currently on the order of meters⁸⁹.

39,000⁹²

Few-mode fiber sensing

It combines the advantages of multi-mode fiber and single-mode fiber sensing.

(1) It is more expensive.

(2) The theorical spatial resolution is limited to the pulse width, which is currently on the order of meters⁸⁹.

6,666¹³⁰

22,123¹³¹

Compression correlation demodulation

Spatial resolution can reach the order of millimeters, and is independent of the sensing distance.

(1) An extra expense (ASE signal generator) for practical application. The bandwidth of the current commercial APD is difficult to meet its requirements.

1,333,333⁵⁴ (Simulation)

Grid Distribution

(1) It does not require additional devices.

(2) It is suitable for some applications.

(1) The spatial resolution is not improved in principle.

(2) A longer sensing optical fiber setting network distribution is required.

3, 750¹³²