Optical receptacle and optical transceiver

An optical receptacle, comprising:

• a fiber stub including an optical fiber, a ferrule, and a first elastic member, the optical fiber including cladding and a core for transmitting light, the ferrule having a through-hole where the optical fiber is fixed, the first elastic member fixing the optical fiber in the through-hole;
• a holder holding the fiber stub;
• and
• a sleeve, the sleeve being configured to hold the fiber stub at one end and hold a plug ferrule at another end,
• the fiber stub having one end surface and another end surface, the one end surface being on a side of the ferrule optically connected to the plug ferrule, the other end surface being on a side opposite to the one end surface,
• the optical fiber including a first portion on the other end surface side, a third portion on the one end surface side, and a second portion between the first portion and the third portion,
• the first portion extending in an axis direction, the axis direction being a direction in which the first portion, the second portion, and the third portion are arranged,
• the second portion extending in the axis direction,
• the third portion extending in the axis direction,
• a core diameter at the first portion being smaller than the core diameter at the third portion,
• the core diameter at the second portion increasing from the first portion side toward the third portion side,
• a change of the core diameter at the first portion in the axis direction being smaller than a change of the core diameter at the second portion in the axis direction,
• a change of the core diameter at the third portion in the axis direction being smaller than the change of the core diameter at the second portion in the axis direction,
• the first elastic member being provided between the optical fiber and an inner wall of the through-hole,
• the holder holding the other end surface side of the fiber stub,
• the sleeve holding the one end surface side of the fiber stub,
• the optical fiber including, at a central portion in the axis direction of the second portion,
• a finest portion where an outer diameter is smallest,
• a change of an inner diameter of the through-hole being smaller than a change of the outer diameter of the optical fiber,
• a thickness of the first elastic member being largest at the finest portion, increasing gradually from the first portion toward the finest portion, and increasing gradually from the third portion toward the finest portion,
• the core diameter at the first portion being 10 μm or less and 0.5 to 4 μm smaller than an incident beam waist, and
• a length of the second portion in the axis direction being 100 μm or more.