| 摘要 |
<p>An optical fiber of spreading an optical pulse in which the ratio (ß<SUB>3</SUB>/ß<SUB>2</SUB>) of the third derivative ß<SUB>3</SUB> to the second derivative ß<SUB>2</SUB>is a negative value, the absolute value of the ratio is large, and the absolute value of the second derivative ß<SUB>2</SUB> is also large. The optical fiber comprises a central core part having a maximum index of refraction N<SUB>1</SUB> and an outside diameter 2a, a depressed part provided around the central core part and having a minimum index of refraction N<SUB>2</SUB> and an outside diameter 2b, and a clad part provided around the depressed part and a maximum index of refraction N<SUB>3</SUB>. The maximum indexes of the central core part, the depressed part, and the clad part satisfy the relation "N<SUB>1</SUB>>N<SUB>3</SUB>>N<SUB>2</SUB>". The relative index difference ?<SUB>1</SUB> of the central core part to the clad part is greater than 1.0%, and the relative index difference ?<SUB>2</SUB> of the depressed part to the clad part is smaller than -0.3%. The second derivative ß<SUB>2</SUB> of the propagation constant ß at a frequency ? is a positive value, the third derivative ß<SUB>3</SUB> of the propagation constant ß at the frequency ? is a negative value, and the ratio (ß<SUB>3</SUB>/ß<SUB>2</SUB>)is -0.002 ps or less.</p> |
