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For desired optical power levels, the bias point and input signal voltage swing can be determined. The bias point is set on the front panel of the Model 1784, and the input voltage swing should be set to give the desired optical power swing. This allows connection to any high-speed 50 Ω SMA compatible signal source without the need for additional bias circuitry.
The VCSEL output is coupled into the internal 50 µm core multimode fiber with a somewhat defocused GRIN lens. This enables Class I laser operation, and also reduces noise in the presence of optical feedback. The coupling also results in excitation of cladding modes which are not stripped internally, so an external mandrel–wrap is advised if cladding modes are unacceptable. You can use either 50 µm or 62.5 µm fiber with the device.
Eye diagrams are a good measure of system performance. The quality of the eye diagram will show if your source has good timing, power levels, proper synchronization, and long-term reliability. If the opening of the eye is larger it gives better certainty that, when the data is sampled, it is a 1 (top of the eye diagram) or a 0 (bottom of the eye diagram). We repeatedly sampled our VCSEL over a period of time at various speeds to obtain the eye diagrams shown above. By pairing Model 1784 VCSEL with Model 1484-A-50 photoreceiver, you can create your own baseline eye diagrams. With that baseline you can insert an optical component between the VCSEL and photoreceiver to test how they would affect data transmission.
The laser is housed in a high–performance microwave housing to minimize distortion of input signals. A bias current is supplied internally, and the high-speed input is connected to a 50-ohm transmission line which is AC coupled to the laser. The VCSEL output is coupled into a 0.1 m, 50 µm core graded–index fiber via a GRIN lens, and internally connected to a front panel FC connector. This ensures clean delivery of the electrical input to the VCSEL chip.
Ultra-High Velocity