An optical system adapted to detect an object including a beam splitting and combing element, a catheter, a focusing element, a shape sensing module and an object detecting module is provided. The catheter sleeves outside an optical fiber, and the optical fiber has at least one fiber Bragg gratings (FBG). The beam splitting and combing element is disposed at one side of the optical fiber. The focusing element is disposed at the other side of the optical fiber. The shape sensing module and the object detecting module are coupled to the beam splitting and combing element. A first light is reflected by the at least one Fiber Bragg gratings, and then transmits to the shape sensing module. A second light transmits to the object and is reflected by the object, and then transmits to the object detecting module. A first wavelength range of the first light is different to the second wavelength range of the second light.一種適於偵測一待測物的光學系統，包含分合光元件、導管、聚焦元件、形變偵測模組以及物體偵測模組。導管設於光纖外，光纖中具有至少一布拉格光纖光柵。分合光元件係配置於光纖的一端。聚焦元件係配置於光纖相對的另一端。形變偵測模組與物體偵測模組係耦接於分合光元件。第一光線被至少一布拉格光纖光柵反射而傳遞至形變偵測模組。第二光線傳遞至待測物後被待測物反射，而傳遞至物體偵測模組。第一光線的第一波長範圍不同於第二光線的第二波長範圍。
