Dummy light module with integrated feedback mechanism

Abstract

A Dummy Light module with an integrated feedback mechanism is disclosed. The Dummy Light module includes a light generation portion, and a polarization handling portion arranged on a same optical path for providing dummy light as output along the optical path. The light generation portion comprises a Gain Flattening Filter and a circulator having a first port a second port and a third port. Further, the circulator is configured to feedback to itself, wherein the circulator is arranged to connect its second (bi-directional) port to a first semiconductor optical amplifier (SOA).

Description

[0001] DUMMY LIGHT MODULE WITH INTEGRATED FEEDBACK MECHANISM

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to optical communication systems and, more specifically, to an optimized Dummy Light module with an integrated feedback mechanism used in Wavelength Division Multiplexing (WDM) transmission links.

[0004] BACKGROUND

[0005] In Wavelength Division Multiplexing (WDM) transmission links, maintaining a stable total input power at the optical amplifier input is essential to avoid unwanted gain transients. Dummy Light modules are used to ensure the stability of the total input power. Traditional dummy light modules, designed for C-band transmission links, utilize cascaded Erbium-Doped Fibre Amplifiers (EDFA). However, with the increasing demand for higher fiber capacity, there is a need to develop the dummy light modules that can operate over wider optical bandwidths.

[0006] Conventionally, certain attempts have been made to generate dummy light, such as cascaded EDFAs or Semiconductor Optical Amplifiers (SOA), which generate dummy light but tend to have large footprints and high costs. Moreover, as the desired optical bandwidth increases, the existing solutions require higher current densities, leading to increased power consumption. Reflective SOAs can reduce power consumption but may introduce a ripple in the optical spectrum, affecting performance.

[0007] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with the conventional dummy light module.

[0008] SUMMARY

[0009] The present disclosure provides a dummy light module with an integrated feedback mechanism. The present disclosure provides a solution to the existing problem of how to optimize the dummy light module for wider optical bandwidths and with reduced cost of production. An objective of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art and provides the optimized dummy light module with an integrated feedback mechanism.

[0010] One or more objectives of the present disclosure are achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.

[0011] The present disclosure provides a dummy light module. The dummy light module includes a light generation portion, and a polarization handling portion arranged on a same optical path for providing dummy light as output along the optical path. The light generation portion includes a Gain Flattening Filter (GFF), and a circulator having a first port, a second port and a third port. The first and third port of the circulator are connected such that the circulator is configured to feedback to itself. The circulator is arranged to connect its second (bi-directional) port to a first semiconductor optical amplifier (SOA).

[0012] Advantageously, by employing the circulator and the GFF, the dummy light module achieves efficient power usage. The feedback loop in the circulator minimizes the need for additional amplification stages, thereby reducing the power consumption of the dummy light module. The use of the circulator in conjunction with the GFF helps in achieving a low ripple in the optical spectrum. The low ripple results in a more stable and uniform output, which is vital for maintaining the performance and reliability of Wavelength Division Multiplexing (WDM) transmission links. The GFF ensures that the gain across the optical spectrum is uniform, which is essential for maintaining the quality of the signal. The improved gain flattening ensures that the dummy light module can support a wide range of wavelengths with consistent performance. The setup of the dummy light module may be easily adapted for use with multiple optical bands [S (short wavelength band), C (conventional band), L (long wavelength band), or any optical band or combinations thereof]. The scalability makes the dummy light module versatile and suitable for various applications, including those requiring wide optical bandwidths. The feedback mechanism provided by the circulator simplifies the overall implementation of the dummy light module.

[0013] In an implementation form, the circulator configured to feedback to itself by its third (output) port being connected to its first (input) port.

[0014] The feedback mechanism stabilizes the light signal by re-amplifying it within the circulator loop. The re-amplification increase significantly the output power of the module. The feedback loop allows for more efficient use of the first SOA, as the same light signal is re-amplified twice within the feedback loop. The reamplification reduces the need for additional amplification stages, thus lowering the overall power consumption of the dummy light module. Compared with reflective semiconductor optical amplifiers, the use of circulator for re-amplification minimizes the optical ripple.

[0015] In accordance with an embodiment, the first SOA is connected to the GFF. The integration of the GFF with the first SOA helps to minimize optical ripple in the output spectrum. The reduction in optical ripple enhances the overall performance of the optical communication system by ensuring a cleaner and more precise signal.

[0016] In an implementation form, the first SOA is connected after the GFF.

[0017] Placing the GFF before the first SOA ensures that the input signal to the first SOA is already flattened in terms of gain, the first SOA receives a more consistent signal, which it can then amplify uniformly, enhancing overall optical signal quality. When the first SOA receives an optical signal with a flattened gain profile, it can operate more efficiently, which minimizes the risk of over-amplification or under-amplification of specific wavelengths, leading to a more efficient use of power and capabilities of the first SOA.

[0018] In an implementation form, the first SOA is connected before the GFF. For practical handling of the elements, the SOA can also be placed before the GFF.

[0019] In an implementation form, the first SOA is connected before the GFF and after another GFF.

[0020] The dual GFF setup helps in minimizing signal distortion. The first GFF reduces the gain variations before amplification, and the second GFF corrects any discrepancies post-amplification. The dual correction mechanism significantly reduces overall signal distortion. The presence of two GFFs helps in minimizing optical ripple in the amplified signal. The first GFF smooths the input signal, and the second GFF further reduces any ripple introduced during amplification, leading to a cleaner output signal.

[0021] In an implementation form, the GFF is arranged on the feedback of the circulator.

[0022] Placing the GFF on the feedback path of the circulator in the dummy light module enhances signal flattening, improves amplification quality, reduces optical ripple, stabilizes output power and ensures efficient power usage.

[0023] In an implementation form, the dummy light module comprises one or two GFFs connected to the first SOA and one GFF arranged on the feedback of the circulator.

[0024] The strategic placement of GFF s ensures consistent gain flattening both before and after amplification, leading to a high-quality output signal with minimal distortion and ripple. The feedback GFF corrects gain variations, maintaining stable output power levels and ensuring reliable performance in various operational conditions. By optimizing the input and output signals of the SOA with GFFs, the dummy light module achieves efficient power consumption, reducing the overall energy requirements and operational costs. The multiple GFFs setup helps manage gain saturation, ensuring the SOA operates within its optimal range and maintaining linearity and performance under varying signal conditions.

[0025] In an implementation form, the light generation portion further includes a Variable Optical Attenuator (VOA) arranged between the circulator and the first SOA.

[0026] The VOA allows for fine-tuning of the input power to the first SOA, enabling precise control over the amplification process. By adjusting the input power to the first SOA, the VOA helps to control the output power level and shape. The stabilization of the output signal is essential for maintaining consistent signal quality, especially in varying operational conditions. Managing the input power with the VOA reduces the stress on the first SOA, potentially extending its operational lifespan by preventing overdriving and excessive heat generation. The VOA provides the flexibility to dynamically adjust the performance of the dummy light module based on real-time network conditions and requirements.

[0027] In an implementation form, the light generation portion further comprises a second SOA arranged after the first SOA.

[0028] Amplifying the signal with the second SOA boosts the overall output power, enabling more robust signal transmission over longer distances. The use of two SOAs allows for more precise gain management, achieving a more uniform and stable amplification profile. The dual SOA configuration provides flexibility to handle a broader range of input signal levels and adjust amplification dynamically. Incorporating the second SOA adds redundancy, improving the reliability and robustness of the dummy light module.

[0029] In an implementation form, the dummy light module further comprises a further second SOA arranged after the first SOA. The two second SOAs is arranged on each of a first branch and the further second SOA is arranged on a second branch, where the light generation portion further comprises a semi-reflective mirror that splits the signal from the first SOA onto the first branch and onto the second branch, whereby the two second SOAs are comprised in the light amplifying portion.

[0030] Splitting the signal from the first SOA into two branches and amplifying each branch with the second SOA significantly increases the overall output power, ensuring more robust and reliable signal transmission. The use of a semi-reflective mirror to split the signal ensures that both branches receive an equal share of the input power, resulting in balanced amplification and uniform signal quality across both paths. The configuration introduces redundancy by having two amplification paths. If one path experiences issues, the other can maintain signal amplification, enhancing the overall reliability of the dummy light module.

[0031] In an implementation form, the light generation portion further comprises a second GFF arranged after the first SOA and before the second SOA.

[0032] Placing a second GFF after the first SOA ensures that any gain non-uniformities introduced by the first SOA are corrected before further amplification, leading to a cleaner, more uniform signal. The second GFF allows for more precise control of the gain profile, ensuring that the signal remains within optimal parameters for the second SOA, which helps in maintaining consistent performance. By flattening the gain between amplification stages, the second GFF minimizes signal distortion and noise, resulting in a higher-quality output. Ensuring a flat gain profile before the signal reaches the second SOA helps in achieving balanced amplification, which is critical for maintaining signal integrity over long distances. The second GFF helps in managing the gain more effectively, which can reduce the overall power consumption and improve the efficiency of the Dummy Light module. The addition of the second GFF provides more flexibility in handling various input signal conditions and tailoring the amplification process to specific requirements, improving the versatility of the dummy light module. In an implementation form, the light generation portion further comprises a second circulator and a third circulator. The second SOA is arranged between a third port of the second circulator and a second port of the third circulator. The third circulator is arranged to feed back to itself, and a third Gain Flattening Filter is arranged on the feedback of the third circulator, where a second port of the second circulator is connected to the amplifier portion.

[0033] The inclusion of multiple circulators and additional GFF ensures that the signal undergoes extensive conditioning and flattening at various stages, resulting in a highly uniform and stable output. The feedback loop created by the third circulator, with the third GFF arranged on its feedback path, ensures a power consumption advantage. The strategic placement of the third GFF in the feedback loop of the third circulator helps to smooth out any residual gain ripple, ensuring a cleaner and more reliable signal output. By distributing the amplification and gain flattening processes across multiple components, the configuration helps in better heat dissipation, preventing overheating and extending the lifespan of the components.

[0034] In an implementation form, the dummy light module is a multiband dummy light module, the light generation portion further comprises a second light generation portion, whereby each light generation portion provides dummy light in one frequency band each.

[0035] The multiband dummy light module can handle multiple frequency bands simultaneously, allowing it to support a broader range of wavelengths and thereby increasing the capacity and flexibility of the optical network. By providing dummy light in different frequency bands, the dummy light module can maintain stable input power across a broader spectrum, optimizing the performance of the WDM (Wavelength Division Multiplexing) systems. Integrating multiple light generation portions into a single module reduces the need for separate dummy light sources for each band, simplifying the system design and reducing the overall equipment footprint. Having separate light generation portions for each frequency band introduces redundancy, ensuring that the failure of one portion does not impact the others, thus enhancing the reliability of the system.

[0036] In an implementation form, the dummy light module is a multiband dummy light module. The light generation portion further comprises a band splitter arranged after the circulator for splitting the bidirectional path of the circulator into a first branch and a second branch. The first branch comprises the first SOA, and the second branch comprises an another first SOA whereby each branch provides Dummy light in one frequency band each.

[0037] The use of the band splitter allows the dummy light module to handle multiple frequency bands efficiently by splitting the bidirectional path into separate branches. The splitting ensures that each branch can be optimized for its specific frequency band. By having dedicated SOAs for each frequency band, the dummy light module ensures optimal amplification and processing of signals in each band, leading to improved overall performance and signal quality. Splitting the paths into separate branches minimizes crosstalk and interference between different frequency bands, enhancing the clarity and reliability of the signal transmission. The modularity introduced by the band splitter allows for flexible allocation and reallocation of frequency bands. The modularity is particularly beneficial in dynamic network environments where the demand for different frequency bands may change. Each branch can be individually optimized for power consumption, leading to more efficient overall power usage, which is essential for maintaining low power consumption in a multiband environment.

[0038] In an implementation form, the polarization handling portion comprises a 50-50 splitter, two mirrors, a polarization rotator and a polarization beam combiner (PBC) to achieve polarization independence.

[0039] The configuration ensures that the output signal is independent of the polarization state of the input light. The independency is essential for maintaining consistent performance in optical communication systems, regardless of the polarization variations that may occur during transmission. The combination of a 50-50 splitter, mirrors, the polarization rotator, and the PBC efficiently manages and manipulates the polarization state of the light. The management of the polarization state ensures optimal use of the optical components, maximizing their effectiveness. In an implementation form, the polarization handling portion is arranged after a last SOA of the light generation portion on the optical path.

[0040] Placing the polarization handling portion after the last SOA ensures that the signal is fully amplified before any polarization adjustments are made, which maximizes the gain from the SOA, resulting in a more robust output signal. With the polarization handling portion positioned after the amplification stages, the output signal remains stable and consistent in terms of polarization. Stability is essential for maintaining signal quality over long distances. Polarization-dependent loss and gain variations are minimized during amplification because the signal is amplified first and then handled for polarization, which results in a more uniform amplification process. The signal quality is improved as polarization effects are managed postamplification, reducing the impact of any polarization mode dispersion or polarization-dependent loss that might occur during amplification.

[0041] It is to be appreciated that all the aforementioned implementation forms can be combined.

[0042] It has to be noted that all devices, elements, circuitry, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application, as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

[0043] Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

[0046] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

[0047] FIG. 1 is a block diagram of a dummy light module, in accordance with an embodiment of the present disclosure;

[0048] FIG. 2 is a block diagram of a dummy light module with a Variable Optical Attenuator (VOA), in accordance with an embodiment of the present disclosure;

[0049] FIG. 3 is a block diagram of a dummy light module with a light generation portion having two bands, in accordance with the embodiment of the present disclosure, in accordance with another embodiment of the present disclosure;

[0050] FIG. 4 is a block diagram of a dummy light module with a light generation portion having three circulators, in accordance with disclosure of present embodiment, in accordance with an embodiment of the present disclosure;

[0051] FIG. 5 is a block diagram of a dummy light module with additional SOAs, in accordance with an embodiment of the present disclosure; and FIG. 6 is a graphical representation of a power spectrum of the dummy light module, in accordance with another embodiment of the present disclosure.

[0052] In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

[0053] DETAILED DESCRIPTION OF EMBODIMENTS

[0054] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.

[0055] FIG. 1 is a block diagram of a dummy light module, in accordance with an embodiment of the present disclosure. With reference to FIG. 1, there is shown a block diagram 100 of the dummy light module 102. The dummy light module 102 includes a light generation portion 104 and a polarizing handling portion 118 arranged on a same optical path 128 for providing dummy light as output 132 along the optical path 128. The light generation portion 104 includes a Gain Flattening Filter (GFF) 106 and a circulator 108 having a first port 110, a second port 112 and a third port 114. The circulator 108 is configured to feedback to itself.

[0056] Further, the circulator 108 is arranged to connect its second (bi-directional) port 112 to a first semiconductor optical amplifier (SOA)116. In accordance with an embodiment, the circulator 108 configured to feedback to itself by its third port 114 being connected to its first port 110. The feedback mechanism stabilizes the light signal by continuously re-amplifying it within the circulator 108. The re-amplification helps in maintaining a consistent output power and reduces fluctuations, leading to more stable and reliable performance. The feedback loop allows for more efficient use of the first SOA 116, as the same light signal is re-amplified multiple times within the feedback loop. This reduces the need for additional amplification stages, thus lowering the overall power consumption of the dummy light module 102. The continuous feedback and re-amplification within the circulator 108 help in minimizing optical ripple.

[0057] The dummy light module 102 is a specialized optical device used in wavelength-division multiplexing (WDM) transmission systems to maintain a stable total input power at the input of an optical amplifier. The stability prevents unwanted gain transients that can disrupt the performance of the transmission link. The dummy light module 102 generates and provides dummy light signals, which are unused or non-data-carrying optical signals, to fill spectral gaps and ensure consistent power levels across the optical spectrum.

[0058] The light generation portion 104 includes elements such as semiconductor optical amplifiers (SOAs), gain flattening filters (GFFs), and circulators. The light generation portion 104 is responsible for generating the initial dummy light signal and ensuring its spectral and power characteristics are suitable for any optical communication system.

[0059] The GFF 106 (interchangeably referred to as a first GFF 106) is an optical device used in fiber optic communication systems to equalize the gain across different wavelengths in a transmission signal. The GFF is employed in systems utilizing optical amplifiers to ensure that the amplification is uniform across the entire operating wavelength range.

[0060] It should be noted that any reference to any GFF in the present disclosure will adhere to the definition of the GFF 106. In accordance with an embodiment, the first SOA 116 is connected to the GFF 106. The integration of the GFF 106 with the first SOA 116 helps to minimize optical ripple in the output spectrum. The reduction in optical ripple enhances the overall performance of the optical communication system by ensuring a cleaner and more precise signal.

[0061] In accordance with an embodiment, the first SOA 116 is connected after the GFF 106. Advantageously, placing the GFF before the first SOA ensures that the input signal to the first SOA 116 is already flattened in terms of gain. The first SOA 116 receives a more consistent signal, which it then amplifies uniformly, enhancing overall signal quality. When the first SOA 116 receives a signal with a flattened gain profile, it operates more efficiently, which minimizes the risk of over-amplification or underamplification of specific wavelengths, leading to more efficient use of power and capabilities of the first SOA 116.

[0062] In accordance with an embodiment, first SOA 116 is connected before the GFF 106. Placing the first SOA 116 before the GFF 106 allows for the initial amplification of the input signal. The initial amplification boost ensures that the signal strength is sufficient before any gain flattening, which is particularly beneficial for weak input signals. The first SOA 116 amplifies the input signal, making it stronger relative to any noise present, which can then be more effectively managed by the GFF 106. By amplifying the signal before it encounters any potential loss or noise added by subsequent components, the overall noise figure of the system can be reduced, which results in a cleaner signal. The GFF 106 can more effectively flatten the gain profile after the signal has been amplified.

[0063] The circulator 108 (interchangeably referred to as a first circulator 108) is a non-reciprocal, multi-port device used in optical communication systems to control the direction of signal flow. The circulator 108 ensures that signals entering any port are directed to the next port in a specific sequence, typically in a clockwise or counterclockwise manner. In accordance with an embodiment, the GFF 106 is arranged on the feedback of the circulator 108. The placement of the GFF 106 on the feedback path of the circulator in the dummy light module 102 enhances signal flattening, improves amplification quality, reduces optical ripple, stabilizes output power, lowers the noise figure, and ensures efficient power usage.

[0064] The first port 110 refers to the initial entry point of the optical signal into the circulator 108 within the dummy light module 102 and serves as the input port where the optical signal is first received before being directed to subsequent ports and different components within the dummy Light module 102.

[0065] The second port 112 refers to the bi-directional port of the circulator 108 within the Dummy Light module 102 and serves as both an input and an output port, allowing the optical signal to be directed to and received from the first SOA 116.

[0066] The third port 114 refers to the output port of the circulator 108 within the dummy light module 102 and serves as the point where the optical signal exits the circulator 108 to be directed to subsequent components, such as the GFF 106 or back to the first port in the feedback configuration.

[0067] The first SOA 116 refers to a device used in optical communication systems to amplify an optical signal. The first SOA 116 operates by using a semiconductor as the gain medium, which is electrically pumped to provide the necessary amplification. The first SOA 116 boosts the power of the optical signal, ensuring that the Dummy Light maintains a stable and sufficient power level. The first SOA 116 may be used in various configurations within the module to enhance performance, reduce power consumption, and maintain a flat output power spectrum.

[0068] Throughout the present disclosure definition of the first SOA 116 applies equally to all other SOAs, regardless of their position or specific role within the dummy Light module 102. The polarization handling portion 118 ensures that the dummy light signal is polarization-independent, meaning it can maintain consistent performance regardless of the polarization state of the light. It often includes devices like splitters, mirrors, polarization rotators, and polarization beam combiners (PBCs).

[0069] In accordance with an embodiment, the polarization handling portion 118 includes a 50-50 splitter 130, two mirrors (i.e., a first mirror 122 and a second mirror 124), a polarization rotator 120 and a polarization beam combiner (PBC) 126 to achieve polarization independence.

[0070] The 50-50 splitter 130 is an optical device used to divide an incoming light signal into two equal parts evenly. The 50-50 splitter 130 splits the optical power of the signal, directing 50% of the power to one output port and 50% to another output port. The 50-50 splitter 130 is used to achieve polarization independence by ensuring that the optical signal is equally split for further processing and recombination within the polarization handling portion 118 of the dummy light module 102.

[0071] The two mirrors (i.e., the first mirror 122 and the second mirror 124), in the context of optical systems, are a reflective surface or device that redirects light by reflecting it. In the dummy light module 102, the two mirrors are used in the polarization handling portion 118 to manage and direct the optical signal paths, ensuring proper alignment and polarization control.

[0072] The polarization rotator 120 is an optical device used to rotate the polarization state of light passing through it by a specific angle. The rotation can be used to match the polarization state of the light to the requirements of subsequent optical components. The polarization rotator 120 adjusts the polarization state of light from linear to circular or circular to linear, depending on the application requirements.

[0073] The PBC 126 is an optical device used to combine two beams of light with different polarizations into a single output beam. The PBC 126 takes two optical signals with orthogonal polarizations and merges them into one, ensuring that the combined output maintains the desired polarization characteristics. The PBC 126 is vital for achieving polarization independence and efficient signal combination within the polarization handling portion 118 of the dummy Light module 102.

[0074] In operation, the first SOA 116 generates the initial light signal along the optical path 128. The light from the left facet of the first SOA 116 enters the first port 110 of the circulator 108. The circulator 108 directs this light from the second port 112 to the third port 114. The light exiting the third port 114 enters the GFF 106. The GFF 106 shapes the spectral profile of the light, ensuring a flat and optimized spectrum. The shaped light from the GFF 106 enters the first port 110 of the circulator 108. The circulator then directs the shaped light back to the second port 112, which is coupled to the first SOA 116, which creates a feedback loop, enhancing the power and efficiency of the light generation. The feedback light re-enters first SOA 116, where it is amplified again. This process continues, building up the light intensity. A portion of the amplified light exits the right facet of the first SOA 116. The light encounters a 50% reflective surface, splitting the beam. The 50 / 50 splitter 130 divides the light into two paths. The two mirrors (i.e., the first mirror 122 and the second mirror 124) direct these paths. The PBC 126 manipulate the polarization states. The PBC 126 recombines the light and produces an output 132 of the dummy light module. The dummy light module 102 allows for the efficient generation of dummy light using a single SOA chip per optical band, with enhanced output power due to the circulator feedback loop and optimized spectral and polarization characteristics.

[0075] In accordance with an embodiment, the polarization handling portion 118 is arranged after a last SOA of the light generation portion on the optical path 128. Advantageously, placing the polarization handling portion 118 after the last SOA ensures that the signal is fully amplified before any polarization adjustments are made. Whole amplification maximizes the gain from the SOAs, resulting in a stronger output signal. With the polarization handling portion positioned after the amplification stages, the output signal remains stable and consistent in terms of polarization. Stability is essential for maintaining signal quality over long distances. The polarization-dependent loss and gain variations are minimized during amplification because the signal is amplified first and then handled for polarization, which results in a more uniform amplification process. FIG. 2 is a block diagram of a dummy light module with a Variable Optical Attenuator (VOA), in accordance with the embodiment of the present disclosure. FIG. 2 is described in conjunction with the elements of FIG. 1. With reference to FIG. 2, there is shown a block diagram 200 which includes a dummy light module 202. The dummy light module 202 includes a light generation portion 204 (which is modified form the light generation portion 104) and the polarizing handling portion 118 arranged on a same optical path 210 for providing dummy light as final output light 212 along the optical path 210. The light generation portion 204 includes the GFF 106 and the circulator 108. In accordance with an embodiment, the light generation portion 204 further comprises a Variable Optical Attenuator (VOA) 206, arranged between the circulator 108 and the first SOA 116. In accordance with an embodiment, the light generation portion 204 further comprises a second SOA 208 arranged after the first SOA 116. The light generation portion 204 further includes a second GFF 214 arranged after the first SOA 116 and before the second SOA 208.

[0076] The VOA 206 is a device used in fibre-optic communication systems to control the power level of an optical signal. The VOA 206 adjust the attenuation (reduction in signal strength) dynamically, allowing precise control over the amount of light passing through. The VOA 206 are commonly used to manage signal power levels, prevent optical receivers from becoming overloaded, and balance signal strengths in multi-channel systems. In an implementation, the VOA 206 may be adjusted manually or electronically, depending on the design and application requirements.

[0077] In operation, the light exits the second port 112 of the circulator 108 and passes through the VOA 206. The VOA 206 adjusts the light intensity to optimize the input to the first SOA 116. The first SOA 116 amplifies the light. The amplified light passes through the second GFF 214 for spectral shaping. The second SOA 208 further amplifies the light. The light then reaches the polarization handling portion 118. Part of the light is reflected into the dummy light module 202 by the 50% reflective surface. The other part of the light goes through the PBC 126 for polarization management. The final output light 212 emerges as the dummy light. The light reflected by the 50% surface enters the first port 110 of the circulator 108. The light is then directed to the third port 114, passes through the first GFF 106, and re-enters the dummy light module 202 at the first port 110. The arrangement allows for high output power, precise spectral control (via two GFFs, i.e. the first GFF 106 and the second GFF 208), and optimized operation via the VOA 206. The dual SOA setup increases power gain and output power, while the polarization handling portion 118 ensures the desired polarization characteristics of the final output light 212.

[0078] It is to be noted that the dummy light module 202 has the same functionalities and components as that of the dummy light module 102.

[0079] Advantageously, the VOA 206 allows for fine-tuning of the input power to the first SOA 116, enabling precise control over the amplification process. By adjusting the input power to the first SOA 116, the VOA 206 helps stabilize the output signal. The stabilization of the output signal is essential for maintaining consistent signal quality, especially in varying operational conditions. By optimizing the input power, the VOA 206 minimizes the introduction of noise and distortion during amplification, which leads to a cleaner, higher-quality output signal. Managing the input power with the VOA 206 reduces the stress on the first SOA 116, potentially extending its operational lifespan by preventing overdriving and excessive heat generation. The VOA 206 provides the flexibility to dynamically adjust the performance of the dummy light module 202 based on real-time network conditions and requirements. The ability to control the input power makes the dummy light module 202 more compatible with a broader range of network configurations and signal levels, enhancing its versatility and applicability.

[0080] FIG. 3 is a block diagram of a dummy light module with a light generation portion having two bands, in accordance with the embodiment of the present disclosure. FIG. 3 is described in conjunction with FIGs. 1 and 2. With reference to FIG 3, there is shown a block diagram 300 of dummy light module 302. The dummy light module 302 is similar in functionalities to the dummy light module 102 and the dummy light module 202. The dummy light module 302 includes a light generation portion 304 which includes a band splitter 306 arranged after the circulator 108 for splitting the second port 112 of the circulator 108 into a first branch 308 and a second branch 310. The first branch 308 includes the first SOA 116, and the second branch 310 includes an another first SOA 116, whereby each branch provides dummy light in one frequency band each. The dummy light module 302 further includes a polarization handling portion 322, which includes a 50-50 splitter 130, two mirrors (the first mirror 122 and the second mirror 124), the polarization rotator 120 for the first branch 308 and a polarization rotator 318 for the second branch 310 and the PBC 126 to achieve polarization independence.

[0081] The band splitter 306 is an optical device used in fibre-optic communication systems to separate an incoming light signal into different frequency bands or wavelength channels. The band splitter 306 works by utilizing filters or other optical components to selectively pass specific wavelengths while directing others along different paths, which allows the signal to be divided and processed separately based on its frequency content.

[0082] In operation, the circulator 108 routes the incoming light signal to the second port 112. The band splitter 306 positioned after the circulator 108, the band splitter 306 divides the incoming light signal into two separate branches. The first branch 308 includes the first GFF 106 and the first SOA 116, designated for the first branch 308. The first GFF 106 helps to flatten the gain profile, ensuring even amplification across the desired frequency range before the signal enters the first SOA 116, which amplifies the signal in the first branch 308. Similar to the first branch 308, the second branch 310 includes the second another GFF 214 and the second SOA 208 designated for the second branch 310. The second GFF 214 performs the same function as the first GFF 106, but for a different frequency band, and the second SOA 208 in the second branch 310 amplifies the signal in the second branch 310. The light from the first branch is rotated by the polarisation rotator 120, and the light from the second branch 310 is rotated by the polarizing rotator 318. After amplification in the two branches, the signals are combined using the PBC 126. The PBC 126 ensures that the signals from the two branches are combined efficiently, with each maintaining its respective polarization state. The combined signal gives output 320.

[0083] In accordance with an embodiment, the dummy light module is a multiband dummy light module, the light generation portion further comprises a second light generation portion, whereby each light generation portion provides dummy light in one frequency band each. Advantageously, the multiband dummy light module can handle multiple frequency bands simultaneously, allowing it to support a broader range of wavelengths and thereby increasing the capacity and flexibility of the optical network. By providing dummy light in different frequency bands, the dummy light module can maintain stable input power across a broader spectrum, optimizing the performance of the WDM (Wavelength Division Multiplexing) systems. Integrating multiple light generation portions into a single module reduces the need for separate dummy light sources for each band, simplifying the system design and reducing the overall equipment footprint. Having separate light generation portions for each frequency band introduces redundancy, ensuring that the failure of one portion does not impact the others, thus enhancing the reliability of the system.

[0084] FIG. 4 is a block diagram of a dummy light module with three circulators, in accordance with the disclosure of the present embodiment. FIG. 4 is described in conjunction with FIGs 1 to 3. With reference to FIG. 4, there is shown a block diagram 400 which includes a dummy light module 402. The dummy light module 402 includes the same components as that of the dummy light module 102 with some additional components in the light generation portion 104, and as a result modified light generation (i.e., a light generation portion 404) is obtained. The light generation portion 404 of the dummy light module 402 further includes a second circulator 406 and a third circulator 414. Further, the second SOA 208 is arranged between a third port 412 of the second circulator 406 and a second port 418 of the third circulator 414, the third circulator 414 is arranged to feedback to itself, and a third GFF 422 is arranged on the feedback of the third circulator 414, and a second port 410 of the second circulator 406 is connected to the amplifier portion.

[0085] The first circulator (i.e., the circulator 108) creates a feedback loop with the first GFF 106 enhances the initial light generation before amplification. The first SOA 116 provides initial amplification. The second GFF 214 shapes the spectrum after the first amplification stage and helps prevent saturation in the following amplifier. The second circulator 406 directs light from the first SOA 116 to the second SOA 216 and also receives and redirects the final amplified light. The second SOA 216 provides additional amplification. The third circulator 414 creates another feedback loop with the third GFF 422 and allows the light to pass through the second SOA 208 twice. The third GFF 422 fine-tunes the spectrum after the second amplification stage. In operation, light enters the first circulator 108, gets shaped by GFF, and is amplified by the first SOA 116. The amplified light is further shaped by the second GFF 214 before entering the second stage. In the second stage, light is amplified by the second SOA 208, then enters a feedback loop through the third circulator 414 and the third GFF 422. The feedback loop allows the light to be amplified twice by the second SOA 216 before exiting. The final amplified light goes back through the second circulator 406 and into the polarization handling potion 118 which generates final output 424 as the dummy light.

[0086] Advantageously, multiple feedback loops (in the first circulator 108 and the third circulator 414) recycle light, reducing the need for high pump currents in the SOAs (i.e., the first SOA 116 and the second SOA 208). The double-pass configuration of the second SOA 208 increases its effective gain without increasing its drive current. Strategic placement of GFFs prevents saturation, allowing SOAs to operate more efficiently. Each GFF (the first GFF 116, the second GFF 214, and the third GFF 422) can have a different spectral profile, which allows for precise control of the spectrum at each stage. The result is a flatter overall output spectrum, crucial for WDM systems.

[0087] In accordance with an embodiment, the dummy light module 402 includes one or two GFFs connected to the first SOA 116 and one GFF arranged on the feedback of the circulator.

[0088] The strategic placement of GFF s ensures consistent gain flattening both before and after amplification, leading to a high-quality output signal with minimal distortion and ripple. The feedback GFF continuously corrects gain variations, maintaining stable output power levels and ensuring reliable performance in various operational conditions. Improved SNR due to effective gain flattening at multiple stages results in a cleaner, clearer signal with reduced optical noise. By optimizing the input and output signals of the SOA with GFFs, the dummy light module achieves efficient power consumption, reducing the overall energy requirements and operational costs. The multiple GFFs setup helps manage gain saturation, ensuring the SOA operates within its optimal range and maintaining linearity and performance under varying signal conditions.

[0089] FIG. 5 is a block diagram of a dummy module with additional SOAs, in accordance with an embodiment of present disclosure. FIG. 5 is described in conjunction with elements from the FIGs 1 to 4. With reference to FIG. 5, there is shown a block diagram 500 of a dummy light module 502 including a light generation portion 104 and an amplifying portion 118 arranged on a same optical path 128 for providing dummy light as output 510 along the optical path 128. The light generation portion 104 includes the GFF 106 and the circulator 108 having the first port 110, the second port 112 and the third port 114. The dummy light module 502 further includes a further second SOA 502 arranged after the first SOA 116. The second SOA 208 is arranged on each of a first branch 504 and the further second SOA 502 is arranged on a second branch 506, where the light generation portion 104 further comprises a semi-reflective mirror that splits the signal from the first SOA 116 onto the first branch 504 and onto the second branch 506, whereby the two second SOAs are present in the amplifying portion 508.

[0090] In operation, the process begins with the GFF 106. The light from the GFF 106 enters the circulator 108 through the first port 110. The circulator directs this light out through the second port 112 along the optical path 128. The light then enters the first SOA 116. The first SOA 116 amplifies the initial light signal, increasing its power. The amplified light from the first SOA 116 encounters a semi-reflective mirror The mirror splits the light into two separate paths the first branch 504 and the second branch 506. In the first branch 504, the split light is further amplified by the second SOA 208. Simultaneously, in the second branch 506, the other portion of split light is amplified by the further second SOA 502. The dual amplification allows for potentially higher power output or redundancy. The amplified signals in both branches pass through the first mirror 122 and the second mirror 124, respectively. The amplified signals from the first branch 504 and the second branch 506 are recombined using the PBC 126. The final dummy light output 510 is produced along the optical path 126. The light from the third port 114 of the circulator back to the GFF 106. This might be used for feedback control or to create a resonant cavity for specific light characteristics.

[0091] Advantageously, splitting the signal from the first SOA 116 into two branches and amplifying each branch with the second SOA significantly increases the overall output power, ensuring more robust and reliable signal transmission. The use of a semi- reflective mirror to split the signal ensures that both branches receive an equal share of the input power, resulting in balanced amplification and uniform signal quality across both paths.

[0092] FIG. 6 is a graphical representation of a power spectrum of the dummy light module, in accordance with an embodiment of present disclosure. FIG. 6 is described in conjunction with the FIGs 1 to 5. With reference to FIG. 6, there is shown a graphical representation 500 of a power spectrum of the dummy light module 102, 202, 302 402 and 502. The graphical representation 600 includes a first curve 602, which is obtained when the dummy light module is operated without circulator (i.e., the first circulator 108, the second circulator 406, the third circulator 414) and a second curve 604 when the dummy light module is operated with the circulator. The power gain is measured in dBm / 0.5nm in an abscissa axis. The wavelength is expressed in nanometres(nm) in an ordinate axis. The power gain measures the power of the optical signal per 0.5 nanometre (nm) of wavelength, expressed in decibels relative to one milliwatt (dBm). In simpler terms, the power gain indicates how much optical power is present within each 0.5 nm segment of the spectrum at various wavelengths. The graphical representation 600 clearly shows that the dummy light module with the circulator has a significantly higher power output across the entire wavelength range. A double-headed arrow 606 indicates a 20 dB difference between the peaks of the first curve 602 and the second curve 604. Both curves (i.e., the first curve 602 and the second curve 604) show a bell-shaped spectrum, which SOAs usually depict. The peak of both curves (i.e., the first curve 602 and the second curve 604) occurs around 1575 nm. The power spectrum with the circulator appears to be slightly broader. The graphical representation 500 demonstrates the substantial improvement in output power (20 dB, i.e., 100 times more powerful) achieved by incorporating a circulator into the optical system of the dummy light module.

[0093] Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.

Claims

1. CLAIMS1. A Dummy Light module (102, 202, 302, 402) comprising: a light generation portion (104) and a polarization handling portion (118, 322) arranged on a same optical path (128) for providing dummy light, DL, as output (132) along the optical path (128), wherein the light generation portion comprises a Gain Flattening Filter, GFF (106), and a circulator (108) having a first port (110), a second port (112) and a third port (114), wherein the circulator (108) is configured to feedback to itself, wherein the circulator (108) is arranged to connect its second (bi-directional) port (112) to a first semiconductor optical amplifier, SOA, (SOA1) (116).

2. The Dummy Light module (102. 202, 302, 402) according to claim 1, wherein the circulator (108) configured to feedback to itself by its third (output) port (114) being connected to its first (input) port (110).

3. The Dummy Light module (102, 202, 302, 402) according to any of claims 1 to 2, wherein the first semiconductor optical amplifier, SOA, (SOA1) (116) is connected to the Gain Flattening Filter, GFF (106).

4. The Dummy Light module (102, 202, 302, 402) according to claim 3, wherein the first semiconductor optical amplifier, SOA, (SOA1) (116) is connected after the Gain Flattening Filter, GFF (106).

5. The Dummy Light module (102, 202, 302, 402) according to claim 3, wherein the first semiconductor optical amplifier, SOA, (SOA1) (116) is connected before the Gain Flattening Filter, GFF (106).

6. The Dummy Light module (102, 202302, 402,) according to claim 4 and 5, wherein the first semiconductor optical amplifier, SOA, (SOA1) (116) is connected before the Gain Flattening Filter, GFF (106) and after another Gain Flattening Filter, GFF.

7. The Dummy Light module (102, 202, 302, 402) according to any of claims 1 to 2, wherein the GFF (106) is arranged on the feedback of the circulator (108).

8. The Dummy Light module (102, 202, 302, 402) according to claim 7 in combination with any of claims 3 to 6, wherein Dummy Light module (102, 202, 302, 402) comprises one or two GFFs connected to the first semiconductor optical amplifier, SOA, (SOA1) (116), and one GFF arranged on the feedback of the circulator (108).

9. The Dummy Light module (102, 202, 302, 402) according to any preceding claim, wherein the light generation portion (104, 204) further comprises a Variable Optical Attenuator, VOA (206), arranged between the circulator (108) and the first SOA (SOA1) (116).

10. The Dummy Light module (102, 202, 302, 402) according to any preceding claim, wherein the light generation portion (104, 204) further comprises a second SOA (SOA2) (208) arranged after the first SOA (SOA1) (108).

11. The Dummy Light module (102, 202, 302, 402) according to claim 10, wherein the Dummy Light module (102, 202, 302, 402) further comprisesa further second SOA (SOA2) arranged after the first SOA (SOA1), wherein the second SOA is arranged on a first branch and the further second SOA is arranged on a second branch, where the light generation portion further comprises a semi reflective mirror that splits the signal from the first SOA (SOA1) onto the first branch and onto the second branch, whereby the two second SOAs are comprised in the amplifying portion.

12. The Dummy Light module (102, 202, 302, 402) according to claim 10, wherein the light generation portion (104, 204) further comprises a second Gain Flattening Filter (214) arranged after the first SOA (116) and before the second SOA (208).

13. The Dummy Light module (102, 202,302,402) according to claim 11 , wherein the light generation (104, 204, 404) portion further comprises a second circulator (406) and a third circulator (414), wherein the second SOA (208) is arranged between a third port (412) of the second circulator (406) and a second port (418) of the third circulator (414), wherein the third circulator (414) is arranged to feed back to itself, and wherein a third Gain Flattening Filter (422) is arranged on the feedback of the third circulator (414), and wherein a second port (410) of the second circulator (406) is connected to the amplifier portion.

14. The Dummy Light module (102, 202, 302, 402) according to any preceding claim, wherein the Dummy Light module is a multiband Dummy Light module, wherein the light generation portion further comprises a second light generation portion, whereby each light generation portion provides Dummy light in one frequency band each.

15. The Dummy Light module (102, 202, 302, 402) according to any of claims 1 to 12, wherein the Dummy Light module is a multiband Dummy Light module, wherein the light generation portion (104, 204,304) further comprises a band splitter (306) arranged after the circulator for splitting the second port (112) of the circulator (108) into a first branch (308) and a second branch (310), wherein the first branch (308) comprises the first SOA (116), and the second branch (310) comprises an another first SOA (316), whereby each branch provides Dummy light in one frequency band each.

16. The Dummy Light module (102, 202, 302, 402) according to any preceding claim, wherein the polarization handling portion (118, 322) comprises a 50-50 splitter (130), two mirrors (122,124), a polarization rotator (120, 318) and a polarization beam combiner (PBC) (126) to achieve polarization independence.

17. The Dummy Light module (102, 202, 302, 402) according to claim 15, wherein the polarization handling portion (118, 322) is arranged after a last SOA of the light generation portion (104, 204, 304, 404) on the optical path (128, 210).

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