DISTRIBUTED RAMAN AMPLIFIER (DRA) SYSTEM AND METHOD THEREOF

Abstract

ABSTRACT DISTRIBUTED RAMAN AMPLIFIER (DRA) SYSTEM AND METHOD THEREOF The present disclosure discloses a Distributed Raman Amplifier (DRA) system (100) that enhances optical signal transmission by dynamically optimizing signal gain and minimizing noise. The system (100) includes an optical fiber (10) through which an optical signal propagates, and a Raman pump module (20) with multiple pump lasers (21, 22, 23) coupled via a wavelength division multiplexer (WDM) (30) to inject pump wavelengths into the fiber. A control unit (40) adjusts the pump power levels based on feedback from a detection module (50), which monitors output signal power using an optical power meter (51). Additionally, an attenuation control module (60) modulates attenuation to further improve the signal-to-noise ratio. This configuration ensures efficient amplification along the optical fiber (10), optimizing signal integrity across varying transmission conditions. The present disclosure also discloses a method (200) for distributed Raman amplifier (DRA) in an optical communication system. Refer Figure 6.

Specification

Description:employed, some embodiments may utilize multiple WDMs, each handling a specific subset of pump lasers. This modular approach allows for additional control over individual pump wavelengths and can be advantageous in complex network setups.
In some aspects of the present disclosure, the Raman pump module (20) may incorporate several additional configurations to enhance flexibility. In a specific embodiment, each pump laser (21, 22, 23) can be paired with separate wavelength division multiplexers (WDMs) to allow independent adjustment of each pump wavelength, offering flexibility in fine-tuning the gain spectrum and adapting to varied signal wavelengths across transmission channels.
In some aspects of the present disclosure, each pump laser (21, 22, 23) in the Raman pump module (20) operates at a unique wavelength within the range of 1420 nm to 1480 nm, which is selected to optimize Raman gain across the transmission wavelength. In some configurations, additional pump lasers operating at intermediate or extended wavelengths may be added to achieve a broader gain spectrum. The pump lasers (21, 22, 23) can be operated in different configurations, including co-pumping (as shown in Figure 3), counter-pumping (as shown in Figure 4), or bidirectional pumping (as shown in Figure 5), to maximize flexibility in amplification control.
In some aspects of the present disclosure, each pump laser (21, 22, 23) operates at the same or similar wavelengths as its counterpart, providing backup in the event of laser failure. In one embodiment, redundant lasers activate only when necessary, extending the lifespan of the active lasers and ensuring consistent system performance.
In some aspects of the present disclosure, the Raman pump module (20) includes a pump combining module (25), which aggregates the output of the pump lasers (21, 22, 23) into a single beam before feeding it into the WDM (30). This setup reduces the complexity of wavelength coupling, helps to optimize the power utilization of the pumps, reducing energy losses and enhancing overall efficiency. Additionally, the pump combining module (25) can be configured to adjust the relative power of each combined laser output to optimize the Raman gain profile.
In some aspects of the present disclosure, the Raman pump module (20) may include multiple WDMs (30) arranged in sequence, each filtering distinct sets of pump wavelengths. This configuration enables better control over the amplification profile, as each WDM (30) can selectively filter certain wavelengths, thereby tailoring the amplification to network-specific requirements.
In accordance with an aspect of the present disclosure, the control unit (40), as depicted in Figure 2A, plays a central role in dynamically adjusting the power levels of the pump lasers (21, 22, 23) in response to feedback from the feedback detection module (50). By implementing a real-time control algorithm based on Raman gain efficiency, the control unit (40) modulates the pump power output to maintain consistent signal gain and minimize noise along the fiber. In one embodiment, the control unit (40) employs machine learning algorithms that adapt over time to changing network conditions. These models allow the system to improve its response to signal variations, leading to more stable amplification and reduced noise levels.
In some aspects of the present disclosure, the DRA system (100) may selectively adjust power levels at certain pump wavelengths to address specific transmission demands. By increasing pump power for shorter wavelengths, the system (100) can provide greater amplification at the leading edge of the Raman gain spectrum, which can help to counterbalance fiber losses that are more pronounced at shorter signal wavelengths.
In some aspects of the present disclosure, the control unit (40) may be programmed with algorithms based on Raman gain efficiency, enabling it to modulate pump power based on the current transmission requirements and network conditions. In some aspects of the present disclosure, the control algorithm uses historical data and predictive models to anticipate fluctuations in the input signal and preemptively adjust the pump power. For example, by learning traffic patterns, the system (1000 can predict when high data demands are likely to occur and adjust the pump power in advance, ensuring stable signal amplification and preventing overloads or power deficits.
In some aspects of the present disclosure, the control unit (40) uses a proportional-integral-derivative (PID) control algorithm to adjust pump power smoothly.
In accordance with an aspect of the present disclosure, the feedback detection module (50), as shown in Figure 1C, monitors the signal power at the output end of the optical fiber (10). The module (50) includes an optical power meter (51) that continuously measures the amplified signal power and quality and sends feedback signals to the control unit (40), enabling the system to compensate for any variations in transmission power or noise levels. This feedback loop enables the control unit (40) to adjust the pump laser (21, 22, 23) powers in real-time, compensating for any fluctuations in signal strength. In one embodiment, the feedback detection module (50) includes a spectrum analyzer for more detailed monitoring of signal characteristics, allowing for advanced optimization of Raman amplification parameters. The optical power meter (51) within the module (50) measures signal power levels, which the control unit (40) then uses to modulate pump power. In alternative embodiments, this module (50) may include additional sensors for monitoring signal integrity, polarization, and spectral distribution, offering a comprehensive feedback mechanism.
In some aspects of the present disclosure, the feedback detection module (50) may include additional sensors, such as a spectrum analyzer, to provide a more comprehensive view of the signal characteristics. This enhanced feedback allows for more detailed control over amplification parameters and is beneficial for high-performance applications.
In accordance with an aspect of the present disclosure, the system (100) further includes an attenuation control module (60) that is connected between the control unit (40) and the optical fiber (10). This module (60) allows for fine-tuning of attenuation levels within the fiber, effectively controlling the noise figure and enhancing the signal-to-noise ratio (SNR). In scenarios where the input signal experiences significant fluctuations, the attenuation control module (60) can dynamically adapt attenuation to maintain stable amplification conditions. This functionality is particularly beneficial in bidirectional pumping configurations, where attenuation control helps balance the gain across both directions.
The DRA system (100) can be configured in multiple pumping modes based on transmission requirements: co-pumping configuration, counter-pumping configuration, and Bidirectional Pumping.
Referring to Figure 3, according to an aspect of the present disclosure, a co-pumping configuration is illustrated. In the co-pumping configuration, the pump lasers inject power in the same direction as the optical signal, enhancing it along the forward path. Co-pumping is energy efficient, as it requires less pump power to achieve the desired amplification. However, it may be less effective at suppressing noise compared to counter-pumping. In other words, the co-pumping propagation module facilitates forward-direction amplification, reducing power consumption by using a lower pump power for effective signal boosting. Co-pumping is particularly suited for networks prioritizing energy efficiency, though it may be supplemented by counter-pumping in noise-sensitive applications.
Referring to Figure 4, according to an aspect of the present disclosure, a counter-pumping is illustrated. In this counter-pumping, pump wavelengths are injected in the direction opposite to the signal propagation. This configuration provides better noise suppression, making it suitable for applications where signal quality is prioritized over energy efficiency. The counter-pumping configuration is beneficial for high-SNR applications, such as long-haul telecommunications, where noise minimization is essential for maintaining signal clarity.
Referring to Figure 5, according to an aspect of the present disclosure, a bidirectional pumping is illustrated. This setup combines co-pumping and counter-pumping, offering balanced gain and noise control for high-performance applications. This approach is ideal for long-distance or high-capacity networks where both amplification and noise management are critical for maintaining signal quality.
For systems employing bidirectional pumping, the attenuation control module (60) can modulate gain in both forward and reverse paths, ensuring balanced amplification. This can prevent power imbalance that might otherwise lead to signal distortions in one direction, maintaining quality in both signal transmission and reception.
The DRA simulation module, illustrated in Figure 6, enables performance evaluation across various configurations and parameters. The parameters includes: signal wavelength= 1550 nm, input signal power = 20 mW, effective Raman gain coefficient = 0.38 W-1km-1, pump attenuation coefficient = 0.3 dB/km, signal attenuation coefficient = 0.25 dB/km, and fiber cross-sectional area= 55 〖μm〗^2. The DRA simulation module enables network designers to model the system's performance across various configurations and conditions. This tool provides data on gain distribution, noise levels, and power consumption, which are crucial for optimizing the DRA system (100) for specific network applications. Simulation data helps to optimize the system design before deployment, ensuring the DRA system meets the specific needs of the network.
Figure 7 illustrates the simulated of output signal power (mW) in a co-pumping configuration against the transmission distance (km). Such simulations help in understanding how different pump configurations impact signal strength over extended distances, providing valuable insights for long-distance transmission planning. The simulation data demonstrates how the output power declines over distance and how the DRA system (100) can be configured to mitigate this loss, extending the reach of the optical signal.
Figure 8 depicts an optical network with multiple pump positions, illustrating how the location of the pump module along the fiber can influence the amplification profile. Placing pumps at strategic intervals along the fiber can enhance the uniformity of gain across the transmission distance. By adjusting the spacing and configuration of pumps, the system (100) can address specific network challenges, such as varying fiber loss characteristics and fluctuating data traffic, providing customized gain control.
In distributed Raman amplification, strategic placement of pump modules is crucial to achieving a uniform gain profile across the optical fiber (10). By placing pumps at multiple intervals along the fiber, as depicted in Figure 8, the system (100) can compensate for signal degradation that typically occurs with distance. In an embodiment, a combination of both co-pumping and counter-pumping sources may be spaced along the transmission path to balance energy efficiency and noise suppression.
The noise figure in a DRA system (100) is influenced by the location and configuration of pump lasers (21, 22, 23). Placing pump sources close to the transmission source can enhance noise suppression by pre-emptively amplifying the signal before degradation begins. Conversely, in certain network applications, placing pumps farther from the source may offer better overall signal-to-noise ratios (SNR) by reducing backscattered noise. An alternative embodiment may include dynamically adjustable pump placement within the optical network. Using modular pump units that can be physically or electronically moved along the fiber allows the system (100) to adapt to changing network demands, such as varying transmission distances or power levels.
Figure 9 shows the relationship between pump power and signal gain in the DRA system (100). This graph highlights the efficiency of the Raman amplification process, illustrating how signal gain increases with pump power up to an optimal point. The data aids in determining the optimal pump power for achieving the desired gain while minimizing energy consumption, especially important in systems where energy efficiency is prioritized.
To analyze the variations in the signal gain concerning pump power, an input signal of 5 mW at the prime central wavelength of 1550 nm with a pump wavelength of 1480 nm, along with increasing pump power, can be observed in Figure 9. It can be observed that the signal gain up to 1000 mW is almost linear. DRA gain is observed in all three pumping configurations at the pump position z = 5 km while the DRA fiber length is L= 20 km. From Figure 9, it can be found that the threshold pump power capacity of the designed DRA compared to EDFA is high [24, 141] and DRA gain is also stabilized in counter pumping configuration [110].
Figures 10A-E present the simulated performance of the DRA system (100) at different pump positions. These simulations underscore the importance of pump placement in achieving consistent gain and highlight the impact of pump power on signal quality across different configurations. The variation in DRA signal gain at the respective wavelength in C- band in multiplexed channel form from 1549 nm to 1560 nm, maintaining the 1 nm wavelength spacing for three pumping configurations, co-pumping, counter-pumping, and bidirectional pumping, is presented. Figures 10A-E illustrate the signal trend of the Raman amplifier, attaining four peaks at wavelengths of 1551 nm, 1554 nm, 1556 nm, and 1560 nm respectively. The flat response of signal gain (dB) at different fiber lengths of simulated DRA at Z = 0, 5 km, 10km, 15km, and 20km.
Pumping configuration Inference
Co-pumping with forward signal Signal gain decreases with extended distance
Counter-pumping with forward signal Signal gain increases with extended distance
Bidirectional pumping Signal gain remains relatively stable and consistent throughout the fiber cable
Table 1: Pumping configuration and inferences
Referring to Figure 11, according to an aspect, the present disclosure provides a method (200) for implementing distributed Raman amplification in an optical communication system is provided. This method (200) involves propagating an optical signal, injecting pump wavelengths, and adjusting pump powers dynamically based on real-time feedback. This approach ensures consistent amplification and high signal integrity.
The method (200) includes the steps of: step (201) - propagating an optical signal at a transmission wavelength through an optical fiber (10); step (202) - injecting Raman pump wavelengths into the optical fiber (10) through a Raman pump module (20), wherein the Raman pump module (20) includes a plurality of pump lasers (21, 22, 23) operating at distinct wavelengths; step (203) - detecting the amplified signal at the output end of the optical fiber (10) via a feedback detection module (50) configured to relay feedback signals; and step (204) - adjusting power levels of the pump lasers (21, 22, 23) dynamically using a control unit (40) based on feedback signals, thereby optimizing Raman amplification along the optical fiber (10) to enhance gain and reduce noise.
In accordance with an aspect of the present disclosure, the method (200) further comprises a step (205) of modulating the wavelength and power of each pump laser (21, 22, 23) in response to variations in the input optical signal power, thereby maintaining a stable gain across the transmission wavelength of the optical signal.
The DRA system (100) offers numerous benefits for modern optical communication networks, including enhanced signal reach, improved noise control, and optimized energy use. Applicable in long-haul networks, data centers, and DWDM systems, the DRA system provides scalable amplification that can adapt to evolving network demands, ensuring reliable, high-quality signal transmission over extended distances.
It should be understood that various forms of the flows shown above may be used, with steps reordered, added, or deleted. For example, the steps described in the present disclosure may be performed in parallel, sequentially or in different orders, and are not limited herein as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved.
Although embodiments or examples of the present disclosure have been described with reference to the accompanying drawings, it is to be understood that the system and methods described above are merely exemplary embodiments or examples and that the scope of the present disclosure is not limited by these embodiments or examples, but only by the claims as issued and their equivalents. Various elements in the embodiments or examples may be omitted or may be replaced with equivalents thereof. Further, the steps may be performed in an order different from that described in the present disclosure. Further, various elements in the embodiments or examples may be combined in various ways. It is important that as technology evolves, many of the elements described herein may be replaced with equivalent elements that appear after the present disclosure.
The implementation set forth in the foregoing description does not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the subject matter described. Although a few variations have been described in detail above, other modifications or additions are possible. In particular, further features and/or variations can be provided in addition to those set forth herein. For example, the implementation described can be directed to various combinations and sub combinations of the disclosed features and/or combinations and sub combinations of the several further features disclosed above. In addition, the logic flows depicted in the accompanying figures and/or described herein do not necessarily require the particular order shown, or sequential order, to achieve desirable results. Other implementations may be within the scope of the following claims.
, Claims:We Claim,

1. A distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission, comprising:
an optical fiber (10) configured to propagate an optical signal at a transmission wavelength from an input end to an output end;
a Raman pump module (20) arranged in optical communication with the optical fiber (10) and configured to inject pump wavelengths into the optical fiber (10), wherein the Raman pump module (20) includes:
a plurality of pump lasers (21, 22, 23) each operable at distinct pump wavelengths and coupled to the optical fiber (10) via a wavelength division multiplexer (WDM) (30);
a control unit (40) operatively connected to the Raman pump module (20) and configured to adjust power levels of each pump laser (21, 22, 23) in real-time based on transmission requirements and feedback signals, thereby ensuring distributed Raman amplification along the optical fiber (10);
a feedback detection module (50) configured to measure power levels of the transmitted signal at the output end of the optical fiber (10) and to relay feedback signals to the control unit (40);
wherein the control unit (40), in response to feedback signals from the feedback detection module (50), dynamically adjusts the pump powers of the pump lasers (21, 22, 23) to optimize signal gain and minimize noise along the optical fiber (10).

2. The distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission as claimed in claim 1, wherein the Raman pump module (20) further comprises:
a pump combining module (25) configured to combine outputs from the pump lasers (21, 22, 23) into a single pump beam before directing it into the wavelength division multiplexer (30).

3. The distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission as claimed in claim 1, wherein the feedback detection module (50) includes:
an optical power meter (51) positioned at the output end of the optical fiber (10) to monitor the power of the amplified signal.

4. The distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission as claimed in claim 1, wherein the control unit (40) is configured to implement an algorithm based on Raman gain efficiency, such that the Raman pump module (20) dynamically adjusts the power levels of the pump lasers (21, 22, 23) in proportion to variations in the input signal.

5. The distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission as claimed in claim 1, wherein each pump laser (21, 22, 23) operates within a predefined wavelength selected to provide distributed Raman amplification across the transmission wavelength of the optical signal.

6. The distributed Raman amplifier (DRA) system (100) for enhancing optical signal transmission as claimed in claim 1, wherein the system (100) further comprising:
an attenuation control module (60) operatively connected between the control unit (40) and the optical fiber (10), configured to modulate attenuation levels in the optical fiber (10) in response to feedback from the feedback detection module (50), thereby reducing noise figure and enhancing signal-to-noise ratio (SNR) of the transmitted signal.

7. A method (200) for distributed Raman amplifier (DRA) in an optical communication system, said method (200) comprising the steps of:
propagating an optical signal at a transmission wavelength through an optical fiber (10);
injecting Raman pump wavelengths into the optical fiber (10) through a Raman pump module (20), wherein the Raman pump module (20) includes a plurality of pump lasers (21, 22, 23) operating at distinct wavelengths;
detecting the amplified signal at the output end of the optical fiber (10) via a feedback detection module (50) configured to relay feedback signals; and
adjusting power levels of the pump lasers (21, 22, 23) dynamically using a control unit (40) based on feedback signals, thereby optimizing Raman amplification along the optical fiber (10) to enhance gain and reduce noise.

8. The method (200) for distributed Raman amplifier (DRA) in an optical communication system as claimed in claim 7, wherein the method (200) further comprising modulating the wavelength and power of each pump laser (21, 22, 23) in response to variations in the input optical signal power, thereby maintaining a stable gain across the transmission wavelength of the optical signal.

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