This letter proposes significant enhancement in optical spatial modulation (OSM) performance by aligning the transmit and receive units. OSM is a recently proposed pulsed modulation technique for indoor optical wireless (OW) communication . In OSM, multiple transmitters are considered where only one transmitter is active at a time and the others are turned off. The incoming bit sequence activates one of the transmit units, i.e. the transmit units are considered as a spatial constellation points and each unique sequence of incoming bits is mapped to one of the constellation points. It is shown that the proposed transmit-receive unit alignments for OSM enhances the performance by more than 14 dB in signal to noise ratio (SNR). In addition, the resultant scheme is shown to be very efficient in terms of power and bandwidth as compared to on-off keying (OOK), pulse position modulation (PPM), and pulse amplitude modulation (PAM).