In the field of dual-mode medical probes, a simple device perfectly meets the double need for dual-modality and sterilization, and provides a sterile, disposable, or sterilizable protective membrane, also called a “glove” or “sock”, equipped with optical fibres. This protective membrane can be slipped onto an ultrasound probe. It therefore ensures both the dual-mode functionality and perfect sterilization of the probe, this being the desired effect. The protective membrane is easy to produce and easy to use.