Optical transmitter and light intensity monitoring method
The present invention provides an optical transmitter and a light intensity monitoring method that provide reliable APC feedback for a semiconductor laser equipped with an SOA. The optical transmitter includes an SOA integrated EA-DFB having a DFB laser, an EA modulator connected to the DFB laser, and an SOA connected to the EA modulator. In the structure of the optical transmitter, a light detector part is disposed forward of the output end side of an SOA part. The light detector part changes part of an output light beam from the SOA part into an electric current and detects light, while guiding the remaining part of the output light beam to a waveguide. With the light detector part disposed forward for the SOA part, it is possible to feed back the output result from the SOA part. Hence, good APC is possible.
1. An optical transmitter comprising:
an SOA integrated EA-DFB including a DFB laser, an EA modulator connected to the DFB laser, and an SOA connected to the EA modulator and a waveguide;
a first light detector for monitoring a signal light beam emitted from the SOA of the SOA integrated EA-DFB, wherein a light detection layer of the first light detector and an absorption layer of the EA modulator or a core layer of the waveguide have the same structure; and
a drive device connected to the DFB laser and the SOA by a single control terminal, for controlling a drive current in accordance with light intensity detected by the first light detector.
2. The optical transmitter according to claim 1 , further comprising a second light detector for monitoring a light beam emitted from the DFB laser, the light beam being monitored without passing through the SOA.
3. The optical transmitter according to claim 2 , wherein the second light detector is disposed to be connected to an end surface of the DFB laser opposite from an end surface thereof connected to the EA modulator.
4. The optical transmitter according to claim 2 , wherein the second light detector is disposed between the DFB laser and the SOA of the SOA integrated EA-DFB.
5. An optical transmitter comprising:
a plurality of SOA integrated EA-DFBs, wherein each SOA integrated EA-DFB includes a DFB laser, an EA modulator connected to the DFB laser, an SOA connected to the EA modulator, a waveguide, and a first light detector for monitoring a signal light beam emitted from the SOA with different oscillation wavelengths of the respective DFB lasers, wherein a light detection layer of the first light detector and an absorption layer of the EA modulator or a core layer of the waveguide have the same structure;
an optical multiplexer for multiplexing a plurality of signal light beams emitted from the SOAs of the plurality of SOA integrated EA-DFBs to output a resultant wavelength-multiplexed light beam; and
a drive device connected to the DFB laser and the SOA of the each SOA integrated EA-DFB by a single control terminal, for controlling a drive current in accordance with light intensity detected by the first light detector respectively.
6. The optical transmitter according to claim 5 , wherein the each SOA integrated EA-DFB includes a second light detector for monitoring a light beam emitted from the DFB laser, the light beam being monitored without passing through the SOA.
7. The optical transmitter according to claim 6 , wherein the second light detector is disposed to be connected to an end surface of the DFB laser opposite from an end surface thereof connected to the EA modulator.
8. The optical transmitter according to claim 6 , wherein the second light detector is disposed between the DFB laser and the SOA of the SOA integrated EA-DFB.
9. An optical transmitter comprising:
an SOA integrated EA-DFB including a DFB laser, an EA modulator connected to the DFB laser and having a lower cladding layer, an absorption layer and an upper cladding layer, an SOA connected to the EA modulator, and a waveguide having a lower cladding layer, a core layer, and an upper cladding layer;
a first light detector having the same layer structure as the EA modulator or the waveguide for monitoring a signal light beam emitted from the SOA of the SOA integrated EA-DFB, wherein a light detection layer of the first light detector is identical to the absorption layer of the EA modulator or a the core layer of the waveguide; and
a drive device connected to the DFB laser and the SOA by a single control terminal, for controlling a drive current in accordance with light intensity detected by the first light detector.