Anonymous
Why do optical transceivers use DFB/EML laser diode chips?
Optical Transceiver Chips
Optical transceiver chips are mainly divided into laser diode chips and photo diode chips, respectively used in laser diodes (such as VCSEL, DFB, EML) for converting electrical signals into optical signals at the transmission end, and in photo diodes (such as PIN, APD) for converting optical signals into electrical signals at the receiver end. They are assembled with filters, metal caps, ceramic tubes and some other components into TOSA, ROSA, or BOSA, and then packaged with PCB, electronic chips and some other sub-assemblies into optical transceiver modules. Optical chips are the core element in optical transceivers. Its performance directly determines attributes including the transmission rate, temperature drift, operation stability and signal-to-noise ratio of optical transceiver modules. In terms of cost, optical chips and sub-assemblies take up 50% to 70% of the total cost of optical transceiver modules, tunable laser, etc.
Passive Optical Component Chips
Optical Laser chips are also used in passive optical components mainly include PLC (Planar Lightwave Circuits) optical splitter chips and AWG (Array Waveguide Grating) chips. PLC optical splitter chips are usually made of two kinds of technology, silicon dioxide optical waveguide and glass optical waveguide. It is composed of multiple branches cascaded to realize the coupling, branching and distribution of optical signals.
AWG chips are composed of two multiport couplers and connected array waveguides, to realize wavelength division multiplexing of N*1, wavelength division demultiplexing of 1*N and wavelength routing of N*N, etc. It is widely used in WDM optical module, ROADM and WSS. Application Scenarios
Optical/Laser chips emit light based on the principle of stimulated emission and can divided into surface-emitting type and edge-emitting type. Surface-emitting type mainly refers to VCSEL (Vertical Cavity Surface-Emitting Laser), suitable for short-distance multi mode application. Edge-emitting type mainly includes FP (Fabry-Perot laser), DFB (Distributed Feedback Laser) and EML (Electro-Absorption Modulated Laser). FP is suitable for application of short to medium reach below 10G, while DFB and EML are suitable for high speed data rate on medium to long reach. EML is currently the main light source for achieving single channel rate of 50G and above, by integrating EAM (Electro-Absorption Modulator) to DFB. Photo diode chips include two main types: PIN(Positive-Intrinsic-Negative Photo Diode) and APD(Avalanche Photo Diode). The former has relatively low sensitivity and is applied to medium and short reach, while the latter has high sensitivity and is applied to medium and long distance.
2 answers
1. Narrow Linewidth: DFB and EML laser diodes have a narrow linewidth, which means they emit light at a specific wavelength with very little variation. This makes them ideal for high-speed data transmission over long distances, as it reduces the chances of signal distortion and interference.
2. High Output Power: DFB and EML laser diodes can produce high output power, allowing for longer transmission distances without the need for additional amplification.
3. Temperature Stability: DFB and EML laser diodes are designed to operate at a specific temperature range, providing stability and reliability in various environmental conditions.
4. Modulation Capability: EML laser diodes have the added advantage of being able to modulate the output signal directly, making them suitable for advanced modulation techniques such as QAM (Quadrature Amplitude Modulation) for higher data rates.
Overall, the use of DFB and EML laser diode chips in optical transceivers helps to ensure high performance, reliability, and efficiency in data transmission applications.
- High Output Power: DFB lasers offer higher output power compared to other laser types, which is crucial for long-distance optical communication.
- Narrow Spectral Width: DFB lasers emit a beam with a narrow spectral width, reducing chromatic dispersion and ensuring signal integrity over extended distances.
- High Modulation Bandwidth: DFB lasers have a high modulation bandwidth, enabling data transmission at high speeds.
- Stable Mode Operation: DFB lasers operate in a single longitudinal mode, minimizing signal distortion and ensuring laser stability.
EML (Electroabsorption Modulated Laser) Diode Chips:
- Low Power Consumption: EML lasers consume less power than DFB lasers, making them energy-efficient for high-volume deployments.
- Direct Modulation: EML lasers can be directly modulated using electrical signals, eliminating the need for external modulators.
- Compact Size: EML lasers are more compact than DFB lasers, which is advantageous for space-constrained applications.
- Low Noise: EML lasers exhibit low noise and high signal-to-noise ratio, minimizing transmission errors.
Combination of DFB and EML:
Optical transceivers combine DFB and EML laser diode chips to achieve the following advantages:
- High Performance and Efficiency: DFB lasers provide high output power and spectral purity, while EML lasers offer low power consumption and direct modulation.
- Long Reach: The combination of DFB and EML enables long-distance transmission with minimal signal degradation.
- Wide Applications: DFB/EML laser transceivers are widely used in telecommunications, data centers, and other high-speed optical networks.
- Cost-Effective: Compared to other laser technologies, DFB/EML transceivers offer a cost-effective solution for high-performance optical communication.
