Optical Internet carries IP traffic over a WDM optical network by taking advantage of huge bandwidth of optical network. The optical burst switching (OBS) was proposed to enhance the low utilization problem of a wavelength routing (or optical circuit switching) and at the same time, relax the technical difficulty in implementing optical packet switching. The optical burst switched networks consists of the edge routers and the core routers. In particular, the edge routers perform the adaptation function, which interfaces between the electronic layer (IP, ATM, SONET) and the optical layer (OBS networks). One of the key functions of the edge router is the burst assembly, in which the data from the electronic layer assembled into a super packet (called a burst). In this paper, we compare three burst assembly schemes: constant assemble time (CAT), variable assemble time (VAT), and adaptive assemble time (AAT). The performance of burst assemble schemes are compared based on the extensive simulations.