Optical transmitter
An optical transmitting unit comprises an integrated optical transmitter module including an LD, a TEC configured to heat or cool the LD, a thermal sensor configured to sense a temperature of the LD, and a package configured to house the LD, the thermal sensor, and the TEC, an MCU, and a temperature detection circuit configured to detect a temperature outside the package. The thermal sensor is thermally coupled with the TEC and is also thermally coupled with the outside of the package, and the MCU defines data output from the temperature detection circuit as an internal temperature when the LD is being energized, and estimates the data of internal temperature on the basis of the temperature detected with the thermal sensor and the data when the LD is not being energized.
1. An optical transmitter having a function of answering an internal temperature to an external device, comprising:
an optical transmitter module including at least one active element configured to generate heat by energization, a thermoelectric element configured to heat or cool the active element, a thermal sensor configured to sense a temperature of the active element, and a package configured to house the active element, the thermal sensor, and the thermoelectric element, the active element being thermally coupled with an outside of the package through a plurality of electric wires connected with a plurality of terminals of the package;
an arithmetic processing circuit configured to control the energization of the active element;
a storage device configured to store data, the data being accessible from the arithmetic processing circuit; and
a temperature detection circuit configured to detect the internal temperature and output data of the internal temperature,
wherein the arithmetic processing circuit stores the data output from the temperature detection circuit to the storage device as the internal temperature when the active element is being energized, and calculates data of the internal temperature based on the basis of both the temperature detected with the thermal sensor and the data stored in the storage device, and stores the calculated data to the storage device as the internal temperature when the active element is not being energized.
2. The optical transmitter according to claim 1 ,
wherein, when thermal resistance between the active element and the temperature detection circuit is defined as RTOSA, thermal resistance between the temperature detection circuit and an outer side surface of the optical transmitter is defined as RTRX, thermal capacity to be heated and cooled by the thermoelectric element is defined as CTOSA, and thermal capacity inside the optical transmitter is defined as CTRX,
[
formula
1
]
1
RTOSA
×
CTOSA
>
1
RTRX
×
CTRX
(
1
)
is satisfied.
3. The optical transmitter according to claim 2 ,
wherein the optical transmitter module includes at least two light emitting elements and at least one drive circuit configured to drive the light emitting elements, as the active elements, and
wherein the light emitting elements and the drive circuit are thermally coupled with the outside of the package through the plurality of electric wires connected with the plurality of terminals of the package, respectively.
4. The optical transmitter according to claim 3 ,
wherein the thermal sensor is electrically connected with the arithmetic processing circuit, and
wherein the arithmetic processing circuit, when calculating the data of the internal temperature on the basis of the temperature detected with the thermal sensor when the active elements are not being energized, utilizes the temperature detected by the temperature detection circuit immediately before stopping the energization of the active elements.
5. The optical transmitter according to claim 4 ,
wherein the active elements are powered by an internal power supply, and the active elements are being energized when the arithmetic processing circuit runs the internal power supply, and the active elements are not being energized when the arithmetic processing circuit stops the internal power supply.
6. The optical transmitter according to claim 5 , wherein
the internal power supply is run by the arithmetic processing circuit when the optical transmitter operates at an operating mode,
the internal power supply is stopped by the arithmetic processing circuit when the optical transmitter operates at a power saving mode, and
whether the optical transmitter operates at the operating mode or at the power saving mode is determined based on an instruction signal.
7. The optical transmitter according to claim 6 ,
wherein the arithmetic processing circuit receives the instruction signal from the external device through a communication bus.
8. The optical transmitter according to claim 1 ,
wherein the optical transmitter module includes at least two light emitting elements and at least one drive circuit configured to drive the light emitting elements, as the active elements, and
wherein the light emitting elements and the drive circuit are thermally coupled with the outside of the package through the plurality of electric wires connected with the plurality of terminals of the package, respectively.
9. The optical transmitter according to claim 8 ,
wherein the thermal sensor is electrically connected with the arithmetic processing circuit, and
wherein the arithmetic processing circuit, when calculating the data of the internal temperature on the basis of the temperature detected by the thermal sensor when the active elements are not being energized, utilizes the temperature detected by the temperature detection circuit immediately before stopping the energization of the active elements.
10. The optical transmitter according to claim 9 ,
wherein the temperature detection circuit and the arithmetic processing circuit are connected through a serial communication bus, and the arithmetic processing circuit receives data of the internal temperature from the temperature detection circuit through the serial communication bus when the optical transmitter operates at an operating mode.
11. The optical transmitter according to claim 10 ,
wherein the active elements are powered by an internal power supply, and the active elements are being energized when the arithmetic processing circuit runs the internal power supply, and the active elements are not being energized when the arithmetic processing circuit stops the internal power supply.
12. The optical transmitter according to claim 11 , wherein
the internal power supply is run by the arithmetic processing circuit when the optical transmitter operates at the operation mode,
the internal power supply is stopped by the arithmetic processing circuit when the optical transmitter operates at a power saving mode, and
whether the optical transmitter operates at the operating mode or at the power saving mode is selected based on an instruction signal.
13. The optical transmitter according to claim 12 ,
wherein the arithmetic processing circuit receives the instruction signal from the external device through a communication bus.
14. The optical transmitter according to claim 1 ,
wherein the thermal sensor is electrically connected with the arithmetic processing circuit, and
wherein the arithmetic processing circuit, when calculating the data of the internal temperature on the basis of the temperature detected by the thermal sensor when the active element is not being energized, utilizes the temperature detected by the temperature detection circuit immediately before stopping the energization of the active element.
15. The optical transmitter according to claim 14 ,
wherein the active element is powered by an internal power supply, and the active element is being energized when the arithmetic processing circuit runs the internal power supply, and the active element is not being energized when the arithmetic processing circuit stops the internal power supply.
16. The optical transmitter according to claim 15 , wherein
the internal power supply is run by the arithmetic processing circuit when the optical transmitter operates at an operating mode,
the internal power supply is stopped by the arithmetic processing circuit when the optical transmitter operates at a power saving mode, and
whether the optical transmitter operates at the operating mode or the power saving mode is selected based on an instruction signal.
17. The optical transmitter according to claim 16 ,
wherein the arithmetic processing circuit receives the instruction signal from the external device through a communication bus.