A fully passive optical signal tapping device named Passive In-line Monitoring (PIM) device is developed to provide and increase the monitoring and maintenance capabilities of Fiber-To-The-Home (FTTH). This device will be permanently installed with the FTTH trunk lines to tap out a small ratio of triple-play signals for monitoring appliance without affecting the service transmission. The PIM device optically splits the full-duplex signals into two portions; 98% maintains in the transmission link, while the other 2% is simultaneously connects to a portable tester unit for identifying the signal presence and direction. Such features also allow the network operators to maintain and operate their network more cost-effectively and offer the end-users with an improved survivability and reliability network, which is continuously monitored 24 h a day and 7 days a week. A PIM device prototype had been successfully developed in this study and implemented in FTTH. The experimental results show the parameters of PIM device are operating wavelength 1310 /1480/1550 nm, operating bandwidth±15 nm, insertion loss≤1.5 dB, return loss≥35 dB and directionality≥55 dB.