An endovascular 
laser treatment device for causing closure of a 
blood vessel uses an 
optical fiber adapted to be inserted into a 
blood vessel. An inner sleeve is arranged around a 
distal portion of the 
optical fiber core such that both distal ends of the inner sleeve and the 
optical fiber core form an enlarged light emitting face. The enlarged emitting face provides substantially lower 
power density while providing the same amount of 
total energy during a treatment session. An outer sleeve arranged around the inner sleeve acts as a spacer to position the light emitting face away from an inner wall of the 
blood vessel. The enlarged light emitting face and the outer sleeve acting as a spacer reduces the possibility of thermal run-away and device damage, and reduce the possibility of vessel perforations, leading to less bruising, post-operative pain and other clinical complications. In yet another aspect of the present invention, a spacer comprises an inner sleeve and an outer sleeve both arranged around a 
distal portion of the core to prevent the 
laser light from traveling laterally and to position the light emitting face away from an inner wall of the vessel. The inner sleeve can be a heat resistive material such as 
ceramic and the outer sleeve can be, for example, a metallic sleeve to provide 
structural integrity and strength to the distal section of the treatment device.