Post SOA Segmentation for OSNR and Noise Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In laser modulation applications, particularly in wavelength multiplexed channels, achieving balanced output light power while minimizing Amplified Spontaneous Emission (ASE) noise and maintaining a high Optical Signal to Noise Ratio (OSNR) is challenging due to the inefficiencies in Semiconductor Optical Amplifier (SOA) placement and biasing, leading to increased power dissipation and reduced OSNR when amplifying late in the modulator chip.
Innovation Solution
The optical device employs a configuration with a first and a second serially connected post SOA unit, where the total SOA length of the first unit is longer than the second, with the first unit maintained at a forward bias of +0.5 V or more, allowing for variable amplification by adjusting the bias voltages across both units to achieve desired output light power levels while minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a post SOA is used to amplify light after modulation components, then power dissipation efficiency is improved, but ASE noise increases and OSNR decreases
Solution Approach 1:
The post SOA is divided into multiple serially connected SOA units with different lengths. The first unit (longer) operates at forward bias to provide stable amplification with low noise, while the second unit (shorter) operates at reverse bias to provide variable attenuation. This segmentation allows the system to achieve both high efficiency and low noise by optimizing each unit's function.
Solution Approach 2:
The invention changes the biasing parameter of the SOA units - specifically maintaining the first unit at forward bias (+0.5V or more) while operating the second unit at reverse bias. This parameter change enables the first unit to provide stable low-noise amplification while the second unit provides controllable attenuation, resolving the contradiction between efficiency and noise.
2Power
If output light power is reduced by reducing incoming light power to post SOA, then output power control is achieved, but OSNR is reduced
Solution Approach 1:
By segmenting the post SOA into two units, the invention enables independent control of amplification (first unit) and attenuation (second unit). This allows output power to be controlled by adjusting the reverse bias on the second unit without reducing the forward bias on the first unit, thereby maintaining OSNR while achieving power control.
Solution Approach 2:
Instead of controlling output power by reducing input power (which reduces OSNR), the invention inverts the approach by using a reverse-biased SOA unit to attenuate the already-amplified signal. This allows power control after amplification, preserving OSNR while achieving the desired output power level.
3Adaptability or versatility
If multiple SOAs are serially connected to provide variable amplification, then power control capability is improved, but device complexity increases
Solution Approach 1:
The invention merges multiple SOA units into a single integrated post SOA structure that provides both amplification and variable attenuation functions. By combining these functions in one compact structure with serially connected units, the invention achieves high power control capability while minimizing the increase in device complexity.
Solution Approach 2:
The serially connected SOA units serve multiple functions: the first unit provides stable amplification, the second unit provides variable attenuation, and together they enable broad power control range. This multi-functionality achieves high adaptability without proportionally increasing complexity, as all units are integrated in a compact arrangement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces ASE noise, maintains high OSNR, and allows for dynamic power adjustment across a broad range, resulting in a compact, cost-effective transmitter with improved power control and reduced noise interference.
Implementation Method 1
a first and a second serially connected post SOA unit, each comprising at least one respective serially connected post SOA... varying respective SOA bias voltages across the post SOAs to achieve a desired amplification level
Implementation Method 2
there will be higher level of Amplified Spontaneous Emission (ASE) noise at the output of the post SOA... this configuration effectively reduces ASE noise
Data Source
AI summary
An optical device comprises a light input, a light modulating means and a light output. The optical device further comprises an optical amplification device arranged to amplify light travelling between said light modulating means and said output. The optical amplification device comprises first and second serially connected post SOA (Semiconductor Optical Amplifier) units, each comprising at least one respective serially connected post SOA segment, which device is arranged to vary a light amplification by varying respective SOA bias voltages across said post SOA segments. A total SOA length of the first post SOA unit is relatively longer than a total SOA length of the second post SOA unit, which is relatively shorter. The optical device is arranged to, during operation using a particular operation program, always keep respective SOA bias voltages across each of the post SOA segments of the first post SOA unit at +0.5 V or more.