With the recent rapid advancements in the Internetof-Things (IoT), one of the applications being developed is thatof smart door lock (SDL) systems. SDL are intended to offerhigh security, easy access and easy sharing. Unlike existing SDLsolutions that mostly use biometrics or crunched RF spectrum, we uniquely propose to use Infrared (IR) optical wireless signal(OWS) using IR light emitting diode (LED) of smartphones. We designed and developed a complete system of Androidsmartphone app including physical layer encoding, a cloud serverand programmable hardware prototypes using Arduino as wellas Raspberry Pi. Optlock includes multi-level security schemesincluding user registration, authentication and authorizationusing one-time-password (OTP). Our extensive experiments show100% accuracy with 1.33 kbps of average data rate is achievedup to 20 meters of distance between a smartphone and a lock. Itallows convenient remote access, easy access control and sharingas well as high security.