OPTICAL AMPLIFICATION APPARATUS FOR A SUBMARINE OPTICAL AMPLIFIER AND RELATED OPTICAL AMPLIFIER

Abstract

Optical amplification apparatus (1) for a submarine optical amplifier (90), the optical amplification apparatus (1) comprising an optical amplification system (2), comprising at least one active component (3), and a DC/DC converter (4) connected to supply the optical amplification system (2), wherein the DC/DC converter (4) comprises a first commutator (5) and a pulse modulator (6) connected to the first commutator (5) for cyclically switching with a duty cycle the first commutator (5) between a closing configuration, in which it can be passed thought by a current, and an opening configuration, in which it cannot be passed thought by the current, characterized in that the DC/DC converter (4) comprises a retroaction circuit (7) comprising, a first differential amplifier (8) connected for receiving, at a first input port, a first signal (100) representative of at least a voltage at output from the DC/DC converter (4) and at input into the optical amplification system (2) and, at a second input port, a first reference signal (201), the first differential amplifier (8) being structured for generating a first error signal (101) representative of a difference between the first signal (100) and the first reference signal (201), a second differential amplifier (9) connected to the first differential amplifier (8) for receiving, at a first respective input port, the first error signal (101) and, at a second respective input port, a second reference signal (201), the second differential amplifier (9) being structured for generating a second error signal (102) representative of a difference between the first error signal (101) and the second reference signal (201), wherein the second error signal (102) is proportional to a deviation of the voltage at output from the DC/DC converter (4) with respect to a nominal working voltage of the optical amplification system (2), in that the first input port of the first differential amplifier (8) and the first respective input port of the second differential amplifier (9) are concordant ports, and in that the pulse modulator (6) is connected to the second differential amplifier (9) for receiving the second error signal (102) and for regulating the duty cycle as a function of the second error signal (102).

Claims

1. An optical amplification apparatus for a submarine optical amplifier, wherein the optical amplification apparatus comprises an optical amplification system, comprising at least one active component, and a DC/DC converter connected to supply the optical amplification system, wherein the DC/DC converter comprises a first commutator and a pulse modulator connected to the first commutator for cyclically switching with a duty cycle the first commutator between a closing configuration, in which it can be passed thought by a current, and an opening configuration, in which it cannot be passed thought by the current, wherein the DC/DC converter comprises a retroaction circuit comprising: a first differential amplifier connected for receiving, at a first input port, a first signal representative of at least a voltage at output from the DC/DC converter and at input into the optical amplification system and, at a second input port, a first reference signal wherein the first differential amplifier is structured for generating a first error signal representative of a difference between the first signal and the first reference signal; a second differential amplifier connected to the first differential amplifier for receiving, at a first respective input port, the first error signal and, at a second respective input port, a second reference signal wherein the second differential amplifier is structured for generating a second error signal representative of a difference between the first error signal and the second reference signal, wherein the second error signal is proportional to a deviation of the voltage at output from the DC/DC converter with respect to a nominal working voltage of the optical amplification system, wherein the first input port of the first differential amplifier and the first respective input port of the second differential amplifier are concordant ports, and wherein the pulse modulator is connected to the second differential amplifier for receiving the second error signal and for regulating the duty cycle as a function of the second error signal.

2. The amplification apparatus of according to claim 1, wherein the first signal is representative of a sum of the voltage at output from the DC/DC converter and of a voltage at input into the DC/DC converter.

3. The amplification apparatus according to claim 1, wherein retroaction circuit comprises an adder connected to the first differential amplifier for receiving, at a first input port, a second signal representative of the voltage at output from the DC/DC converter and, at a second input port, a third signal representative of a voltage at input into the DC/DC converter (I), and wherein said, wherein the adder is structured to operate a sum of the second and third signal and generate the first signal as a function of the sum of the second and third signal.

4. The amplification apparatus according to claim 1, wherein the first commutator is selected in the group: MOSFET transistors, IGBT transistors or BJT transistors.

5. The amplification apparatus according to claim 1, wherein the pulse modulator is selected in the group: pulse width modulators or pulse frequency modulators.

6. The amplification apparatus according to claim 1, wherein the DC/DC converter comprises an inductor connected upstream of the first commutator, wherein the inductor is structured for storing current when the first commutator is in the closing configuration and for supplying current when the first commutator is in the opening configuration.

7. The amplification apparatus according to claim 1, wherein the DC/DC converter comprises a second commutator connected downstream of the first commutator, wherein the second commutator is structured for allowing a current passage towards said optical amplification system when the first commutator is in the opening configuration and for blocking a current return towards the first commutator when the first commutator is in the closing configuration, wherein the second commutator is selected in the group: classic diodes, Schottky diodes, MOSFET transistors.

8. The amplification apparatus according to claim 1, wherein the DC/DC converter comprises a second commutator connected downstream of the first commutator and an accumulator connected downstream of the second commutator, wherein the accumulator is structured for storing current when the first commutator is in the opening configuration and for supplying current when the first commutator is in the closing configuration, wherein the accumulator is a capacitor.

9. The amplification apparatus according to claim 1, comprising an equalizing filter connected upstream of the DC/DC converterfor levelling a current at input into the DC/DC converter and wherein the equalizing filter is selected in the group: capacitors, low-pass filters.

10. A submarine optical amplifier comprising: a vessel having a housing cavity; and an optical amplification apparatus according to claim 1 housed in the housing cavity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] FIG. 1 schematically shows an optical amplification apparatus for a submarine optical amplifier of known type;

[0054] FIG. 2 schematically shows an optical amplification apparatus for a submarine optical amplifier according to an embodiment of the present invention;

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

[0055] The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments of the present invention, presented by way of non-limiting example, with reference to the attached figures.

[0056] FIG. 2 shows a submarine optical amplifier 90, comprising a vessel 91 (only schematically shown) having a housing cavity wherein an optical amplification apparatus 1 according to the present invention is housed. The power supplying of the optical amplification apparatus takes place remotely by the electric conductor of the optical transmission cable which is connected to the power supplying source 50 (PFE, “Power Feeding Equipment”).

[0057] The optical amplification apparatus 1 comprises an optical amplification system 2 comprising a plurality of active components, indicated as a whole by the reference number 3, used for performing the processing (amplification, routing, regeneration etc.) of the optical signal. The amplification system is herein not further described and illustrated as known per se.

[0058] The optical amplification apparatus 1 comprises a DC/DC converter 4 connected to the optical amplification system 2 to supply the active components. Typically, the amplification system also includes further DC/DC converters (not shown) for the adaptation of the voltage at input into each component and/or group of components.

[0059] Exemplarily the optical amplification apparatus comprises an equalizing filter 20 connected upstream of the DC/DC converter 4.

[0060] Exemplarily the equalizing filter 20 consists of a single capacitor. Alternatively, not shown, the equalizing filter can consist of a plurality of capacitors connected in parallel to each other (for example for increasing the reliability and/or reducing costs).

[0061] Preferably the DC/DC converter 4 comprises a first commutator 5, exemplarily a MOSFET transistor.

[0062] Preferably the DC/DC converter 4 comprises a pulse modulator 6, exemplarily a pulse width modulator (PWM).

[0063] Preferably the pulse modulator 6 is connected to the first commutator 5 for cyclically switching with a duty cycle the first commutator between a closing configuration in which can be passed through by a current and an opening configuration in which cannot be passed through by the current. In an ideal circuit, the duty cycle is exclusively regulated according to the power variation required by the optical amplification system 2. On the other hand, considering a real circuit, the variation of the duty cycle is also influenced by other factors, such as the voltage drop across the diode 11 and the voltage drop on the drain of the MOSFET transistor 5, which are both variable as a function of the power supplying current and the working temperature.

[0064] The propagation direction of the current, to which the terms “upstream” and “downstream” hereinafter used refer to, is indicated by the reference number 400.

[0065] Exemplarily the DC/DC converter 4 shown in FIG. 2 is a “stepup”-type converter, which comprises: [0066] an inductor 10, exemplarily connected upstream of the first commutator 5; [0067] a second commutator 11, for example a schottky diode, exemplarily connected downstream of the first commutator 5. In case, for example, the DC/DC converter is used in a synchronous rectification configuration for improving the electric efficiency of the amplification apparatus, the second commutator could be a MOSFET transistor (not shown); [0068] an accumulator 12, for example a capacitor, exemplarily connected downstream of the second commutator 11.

[0069] Alternatively, to a “stepup”-type DC/DC converter, it is possible using, among others, “forward”-type DC/DC converters, “Flyback”-type DC/DC converters or “SEPIC”-type DC/DC converters (not shown).

[0070] In the following paragraphs, the power supplying mode of the optical amplification system 2 in an optical amplification apparatus that uses a “stepup”-type DC/DC converter is described.

[0071] The power supplying mode of the optical amplification system 2 depends on the configuration assumed by the MOSFET transistor 5. When the MOSFET transistor 5 is in the closing configuration (in which is comparable to a short circuit) the impedance of the MOSFET transistor 5 is much lower than the impedance of the components (i.e., the diode 11, the capacitor 12 and the optical amplification system 2) downstream of the transistor 5, thus causing substantially all the power supplying current to flow inside the MOSFET transistor 5 (except of small leakage currents which are absorbed by the circuit downstream of the MOSFET transistor). Across the inductor 10 there is a positive voltage difference (voltage at input into the inductor > voltage at output from the inductor) and the passage of the current inside the inductor 10 entails a variation (e.g., an increase) of the magnetic field around the coils of the inductor 10, with the consequent storage of electric energy as magnetic energy. The optical amplification system 2 is powered by the capacitor 12 which supply electric energy stored during the time interval wherein the MOSFET transistor 5 is in the opening configuration. The supplying of the energy stored by the capacitor 12 causes a lowering of the cathode voltage (in FIG. 2 the right end) of the diode 11 with respect to the anode voltage (in FIG. 2 the left end) of the diode 11, preventing a current return towards the MOSFET transistor.

[0072] When the MOSFET transistor 5 is in the opening configuration (in which is comparable to an open circuit), a variation of the magnetic field around the coils of the inductor 10 occurs and a polarity inversion across the inductor 10 (voltage at input into the inductor < voltage at output from the inductor, due to the reverse electro-motive force phenomenon). This polarity inversion allows a discharge of the energy stored inside the inductor 10 during the closing configuration of the MOSFET transistor 5, and parallelly an increase in the anode voltage of the diode 11 such as to exceed the cathode voltage value of the diode 11 which allows the current passage towards the optical amplification system 2. Part of the supplied current is stored inside the capacitor 12 for allowing the power supplying of the optical amplification system 2 when the MOSFET transistor 5 is in the opening configuration.

[0073] Preferably the DC/DC converter 4 comprises a retroaction circuit 7 which comprises: [0074] a first differential amplifier 8 connected for receiving at a first input port, for example the inverting port, a first signal 100, exemplarily representative of both a voltage at output from the DC/DC converter and a voltage at input into the DC/DC converter, and at a second input port, for example the non-inverting port, a reference signal 201. Preferably the first differential amplifier 8 is structured for generating a first error signal 101 representative of a difference between the first signal 100 and the reference 201; [0075] a second differential amplifier 9 connected to the first differential amplifier 8 for receiving at a respective first input port, for example the inverting port, the first error signal 101 and at a respective second input port, for example the non-inverting port, the reference signal 201. Preferably the second differential amplifier 9 is structured for generating a second error signal 102 representative of a difference between the first error signal 101 and the reference signal 201, wherein the second error signal 102 is proportional to a deviation of the voltage at output from said DC/DC converter 4 with respect to a nominal working voltage of the optical amplification system 2.

[0076] In one not shown alternative embodiment the reference signal at input at the second port of the second differential amplifier is different from the reference signal at input at the second port of the first differential amplifier.

[0077] Preferably the pulse modulator 6 is connected to the second differential amplifier 9 for receiving the second error signal 102 and for regulating the duty cycle as a function of the second error signal.

[0078] Exemplarily the retroaction circuit 7 also comprises an adder 13, for example of analogic type, connected to the first differential amplifier 8 for receiving at a first input port a second signal 103 representative only of the voltage at output from the DC/DC converter 4, and at a second input port a third signal 104 representative of the voltage at input into the DC/DC converter 4. For example, the second and third signals are voltage values respectively obtained by scaling (e.g., by a resistive divider) the voltage at output from the converter and the voltage at input into the converter.

[0079] Exemplarily the adder 13 is structured to operate a sum of the second 103 and third signal 104 and generate the first signal 100 as a function of the sum of the second 103 and third signal 104.

[0080] In use, as described above, the retroaction circuit 7 allows keeping the voltage at output from the DC/DC converter 4 at a constant value, equal to the nominal working voltage of the optical amplification system 2. The retroaction circuit 7 is made so that when the value of the voltage at output from the DC/DC converter 4 is equal to the value of the nominal working voltage of the optical amplification system 2, the first signal 100 assumes, for example, a reference value that, through the two difference operations, allows obtaining the first 101 and the second error signals 102, both also having a respective reference value for setting the duty cycle to the desired value.

[0081] In case, for example, the voltage at output from the DC/DC converter tends to decrease with respect to the nominal working voltage of the optical amplification system, the first signal 100 would have a lower value than the aforesaid reference value. This would generate at the output of the first differential amplifier 8 a first error signal 101 having a value greater than the respective reference value (since the first signal is compared with the reference signal which has a constant value). The subsequent difference operation performed by the second differential amplifier 9 would then generate a second error signal 102 having a lower value than the respective reference value, since the difference is performed with respect to the reference signal 201 having a constant value. This second error signal 102 having a value lower than the respective reference value would command a decrease in the duty cycle which in a stepup-type DC/DC converter, wherein the relationship between voltage at input and voltage at output can be approximated with the formula Vin=Vout*(1-D), would lead to an increase in the voltage at input into the converter and consequently an increase in the voltage at output from the DC/DC converter which would tend to return to the value of the nominal working voltage of the optical amplification system 2.

[0082] In case, on the other hand, the voltage at output from the DC/DC converter tends to increase with respect to the nominal working voltage of the optical amplification system, the duty cycle would increase and a lowering of the voltage at output from the converter would occur.