An optical communication system can increase a minimum optical reception level or the number of connectable optical receivers by controlling optical output levels of its optical transmitter. The optical communication system includes the optical transmitter having an optical variable splitting controller for splitting received light into N parts and supplies them to N optical fibers, and N optical receivers for receiving the signals sent via the N optical fibers. The optical variable splitting controller regulates its optical output levels to be supplied to the N optical fibers by controlling the optical coupling ratios. For example, the optical variable splitting controller may regulate its optical output levels by controlling its optical coupling ratios such that optical reception levels become equal for all the N optical receivers.