This application discloses an optical splitting apparatus, an optical splitting system, a passive optical network, and an optical fiber fault detection method. The optical splitting apparatus includes a first optical splitting unit, a plurality of first optical path processing units, and a second optical path processing unit. The first optical splitting unit includes a first port and a plurality of second ports, and the first port is separately connected to the plurality of second ports. The first optical path processing unit includes a third port, a fourth port, and a fifth port, and the fifth port is separately connected to the third port and the fourth port. The second optical path processing unit includes a sixth port, a seventh port, and an eighth port, and the sixth port is separately connected to the seventh port and the eighth port. The third port is connected to the second port through a first optical fiber, the fourth port is connected to a second optical fiber, and the fifth port is connected to a branch fiber. The sixth port is connected to a feeder fiber, the seventh port is connected to the first port through a third optical fiber, and the eighth port is connected to a fourth optical fiber.