Rather than using a single powerful beam, the Pulse Laser fires a series of rapid pulses. Like all Pulse Lasers, the Medium Pulse Laser has a shorter beam duration time than their standard counterparts.
When compared to the standard Medium Laser, the pulse version outputs seventeen percent more damage in a shorter period, which also increases potential concentration of that damage to a single location of an enemy 'Mech. However, they weigh twice as much, output twenty percent more heat, and have a significantly shorter range than the standard laser.
In general, the Medium Pulse Laser is usually used when the pilot has tonnage to spare and wishes to maximize their short-range damage output as much as possible.