A type of light source that resembles a light-emitting diode (LED) in structure, although much more difficult and expensive to manufacture, much less durable, and much more capable. Laser diodes are associated with more expensive and complex supporting electronics, but generally have much faster cycle times and, therefore, offer much more bandwidth. Diode lasers offer significant mechanical and optical coupling efficiency.Therefore, they can mechanically couple to a singlemode fiber (SMF) and can tightly focus a high-speed optical signal for presentation to its core, which has a diameter of only 5