The difference is usually price, feature set, and size.
An instrument typically has a front panel with knobs and button adjustments and some form of display to track how the laser diode is operating. These can all be automated with computer control via USB, RS-232, RS-485, or GPIB. An instrument is usually powered by AC, not a DC power supply.
By our defi nition, a module doesn’t include the display or power supply, and has the minimum required adjustments. To monitor status, an external voltmeter measures voltage and the module datasheet provides a transfer function to convert the voltage to actual laser diode current or photodiode current.
A component is further stripped down, with no moving parts. External resistors or capacitors set operating parameters. Safety features are common to all three forms. Usually modules can sit on a benchtop or be integrated into a system using cables. Components mount directly to a printed circuit board (PCB) with plate-through or surface mount (SMT) pins. Two rows of pins are referred to as DIP packaging (dualin-line), while a single row of pins is called SIP packaging (single-in-line).
A variety of off-the-shelf controllers are available in both instrument and OEM packages. Some vendors are blurring the boundaries, for example, offering USB control of components as mini-instruments.Packaging of components and modules includes proper heatsinking of the circuit elements (or guidance on how the device should be heatsunk) and usually includes the appropriate cabling to the laser diode and power supply. Instruments include a power cord and user access inside the case is not necessary.