They have an extremely sensitive performance, label-free, capabilities of multi analytes detection, which can be used in medical diagnosis, environmental safety, drug detection.
These are a couple of papers you might find very useful in this matter.
Mohammad Al Mahfuz if you mean the PCF biosensors that operate in optical length, the amount of confinement loss is very important, because it directly related to the sensor length that you can use during experiment. If you have a high confinement loss then you will get a very short fiber working length which sometimes very difficult to handle.