Medical device systems and methods for making and using medical device systems are disclosed. An example medical device system may include a guidewire. A pressure sensor assembly may be disposed within the guidewire. The pressure sensor assembly may include a pressure sensor and a first optical fiber coupled to the pressure sensor. The first optical fiber may have a first outer diameter. A cable may be coupled to the guidewire. The cable may include a second optical fiber. The second optical fiber may have a second outer diameter greater than the first outer diameter.