What is an optical module??Understanding the Working Principle and Core Chip of Optical Modules in One Article
Optical modules are core components in fiber optic communication networks.,Responsible for converting between electrical and optical signals。This article starts from basic principles,Explain how the optical module works.、What's inside?、How to classify and select models,And whyDFBlaser chip——Especially1310nmand1550nmwavelength——This determines the upper limit of the optical module's performance.。
If you have ever been curious,How do data centers move hundreds of servers per second between rows of servers?GBData transmission speed,The core of the answer isoptical module(optical transceiver module)。
These tiny devices are only the size of a finger.,Plug into each switch、Routers and servers,Silently performing bidirectional conversion between electrical and optical signals。No optical module,Fiber optic communication networks will not work.——It's like having no translator.,People who speak two languages cannot communicate.。
Working principle of optical modules
The function of an optical module is quite simple.:Convert electrical signals into optical signals and send them out.,Then convert the received optical signal back into an electrical signal.。Specifically, it can be broken down into three steps.:
- electricity→Light conversion(Sending end)。The switch or server sends an electrical signal.,After entering the optical module,From the internal laser chip(Laser Diode)Modulate an electrical signal into an optical signal of a specific wavelength.。
- Fiber optic transmission。The modulated optical signal enters the optical fiber,Propagates via total internal reflection in optical fiber.。According to fiber type and module specifications,Transmission distance from100Rice100Several kilometers。
- Light→Electrical conversion(receiver)。Photodetector in the remote optical module(Photodetector)After receiving the light signal,Restore it to an electrical signal,For receiving equipment processing。
The entire process is completed at the nanosecond level.,Timing accuracy reaches the picosecond level。Moreover, sending and receiving occur simultaneously.——The optical module has independent transmit and receive channels.,Or through wavelength division multiplexing(WDM)Bidirectional communication using different wavelengths on the same optical fiber。
Internal structure of optical module
Although the optical module is small,It integrates multiple precision components internally.。Understanding these components helps explain why different modules have such large price differences.,And what factors determine transmission performance?。
TOSA——Light emitting component
TOSA(Transmitter Optical Sub-Assembly)It is the transmission core of the optical module.,The most crucial thing islaser chip。Laser chips convert electrical current into coherent light.,Equivalent to optical module"Light bulb"。
High-performance optical modules useDFB(Distributed feedback)Laser。Compared to ordinaryFPLasers are different,DFBThe laser integrates a Bragg grating.(Bragg Grating),Only one longitudinal mode oscillation is allowed.,The output spectrum is extremely narrow(The line width can be less than0.1nm),The wavelength is very stable。This is a long distance、The basis of high-speed transmission。
TOSAIt also includes a monitoring photodiode.(Real-time monitoring of output power)、thermoelectric coolerTEC(Temperature-controlled stable wavelength)and drive control circuit。
ROSA——Optical receiver component
ROSA(Receiver Optical Sub-Assembly)Responsible for converting the received optical signal back into an electrical signal。The core component is a photodetector.:
- PINphotodiode:Low cost、Low operating voltage,Suitable for short-distance transmission。
- APD(Avalanche photodiode):Provided through the avalanche multiplication effect6~10 dBAdditional sensitivity,It is the preferred choice for long-distance optical modules.。
The weak current signal output by the detector,First, it passes through a transimpedance amplifier.(TIA)Converted to voltage signal,The signal is then shaped into a clean digital signal by a limiting amplifier.。
BOSA——Low-cost two-way solution
For single-fiber bidirectional(BiDi)optical module,Transmit and receive share a single optical fiber。at this timeTOSAandROSAmerged into oneBOSA(Bidirectional Optical Sub-Assembly),Simultaneous transmission and reception within a single package。BOSAThe solution can save30%~40%Module cost,existFTTH(Fiber to the Home)Widely used in point-to-point access networks。
DFBThe laser chip is mounted on a butterfly-shaped package substrate.——The core light source device inside the single-mode optical module。
Classification of optical modules
According to fiber type:single-mode vs Multimode
This is the most basic classification method.:
| Comparison items | Single-mode optical module | Multimode optical module |
|---|
| Fiber type | single-mode fiber(fiber core~9µm) | Multimode fiber(fiber core50µmor62.5µm) |
| Transmission mode | Single mode | Multiple modes |
| Operating wavelength | 1310nm or 1550nm | Usually 850nm |
| laser source | DFBLaser or FPLaser | VCSEL or LED |
| Transmission distance | 10km ~ 150km+ | The farthest2km |
| Typical applications | Metropolitan Area Network、Long-distance trunk lines、Data Center Interconnect | Inside the computer room、Data center rack interconnection |
| Fiber optic color | Yellow outer skin | orange color(OM1/OM2)Or light blue(OM3/OM4) |
According to operating wavelength
Two commonly used wavelength windows in single-mode optical modules:
- 1310nm(Oband):In standard single-mode fiber, dispersion is close to zero.,Suitable for medium-distance transmission(The farthest40km)。yes5GPrequel、Enterprise Network andPONThe mainstream choice for passive optical networks。
- 1550nm(Cband):Lowest attenuation among quartz optical fibers(about0.2dB/km),It is the preferred choice for long-distance trunk lines and ultra-long-distance transmission.,It is also coherent optical communication and wavelength division multiplexing.(WDM)The system's standard wavelength。
Why these two wavelengths??There are two types of quartz optical fibers."Golden Window"——1310nmMinimal dispersion,1550nmMinimum loss。that's why1310nmand1550nmofDFBLaser chips are the most widely used light source in single-mode optical communication.。
Common packaging forms
Optical modules have standardized packaging forms.(By multi-source protocolMSAdefinition),The following are some of the most common types in the industry:
| Packaging | Maximum speed | Typical applications |
|---|
| SFP | 1 Gbps | Gigabit Ethernet、Telecommunications access network |
| SFP+ | 10 Gbps | Enterprise Switch、10 Gigabit Ethernet |
| SFP28 | 25 Gbps | 5GPrequel、Data CenterToRswitch |
| QSFP+ | 40 Gbps | Data center aggregation layer |
| QSFP28 | 100 Gbps | Data center leaf spine architecture、DCIinterconnected |
| QSFP56 | 200 Gbps | High densityDCI、High-performance computing cluster |
| QSFP-DD / OSFP | 400~800 Gbps | AITraining Cluster、backbone network |
current,400GOptical modules have been widely deployed in hyperscale data centers.,800GOptical modules enter the stage of large-scale commercial use,1.6TOptical modules begin small-batch production——The driving force mainly comes fromAITraining workloadGPUExplosive demand for internet bandwidth。
Core application scenarios of optical modules
Data Center
The largest application market for optical modules。Data center interior,Optical modules connect servers and switches(Multimode short-range solutions are typically used.)；Between different buildings and different parks,This necessitates a single-mode long-distance solution.。Interconnection between data centers(DCI)Use a single-mode optical module in conjunction withDWDMtechnology,Distance is reachable10~80km。
Telecommunications Network
from5GBase station fronthaul to metropolitan area core network,Optical modules form the physical layer foundation of every bearer network.。25GSingle-mode optical module(use1310nm DFBLaser)yes5GThe mainstream approach to prequels,100G/200G/400GCoherent optical modules handle backbone traffic。
Enterprise Network
high school、Hospital、government agencies、Large enterprises are building campus networks.,Optical modules are used for backbone interconnection between buildings and high-speed server access.。
Fiber Optic Sensing and Industrial Applications
In addition to communication,DFBLasers are also widely used in distributed fiber optic sensing.(temperature、strain、Vibration monitoring)、Gas detection(TDLASLaser spectroscopy)、Laser ranging(LiDAR)and medical imaging and other fields。
Optical module inserted into network switch panel——Behind every fiber optic connection,They are all undergoing high-speed electro-optical conversion.。
What parameters should be considered when selecting a model??
In actual projects, optical modules are selected.(or laser chip),The following parameters are the most critical.:
- Laser source quality:DFBThe narrower the linewidth of the laser(< 0.1nm)、The higher the edge mode suppression ratio(SMSR > 45dB),The cleaner the signal,The longer the transmission distance,The lower the bit error rate。
- Temperature stability:WithTECThe temperature control module can-5°Carrive+70°CMaintain wavelength and power stability within the range——This must be considered when deploying outdoor telecommunications.。
- Reliability Standards:conform toTelcordia GR-468-COREReliability standards andRoHSEnvironmentally friendly components,More reliable in long-term operation。
- Power consumption:High-density data center deployment,Thousands of modules running simultaneously,The difference in power consumption directly affects the cost of heat dissipation andPUE。
- compatibility:Multi-source protocol(MSA)Compliance ensures interoperability with switches and routers from different vendors.。
DFBlaser chip:optical module"heart"
The core of each single-mode optical module,They are all laser chips。For long distances、For high-performance single-mode optical modules,DFB(Distributed feedback)LaserIt is currently recognized as the industry's standard light source.。
With simpleFP(Fabri-Perlo)Lasers are different,DFBThe laser integrates a Bragg grating structure inside the chip.。This grating acts like a precise wavelength filter.,Only allow light oscillation amplification at specific wavelengths,Thus, a single longitudinal modulus is output.、extremely narrow linewidth laser。Actual effect:
- Spectral linewidth can reach 0.1nm(FPLasers typically > 3nm)
- Side mode suppression ratio > 45dB(Almost no stray wavelengths)
- Wavelength drift with temperature only ~0.1nm/°C(FPlaser approximately 1nm/°C)
- exist40kmMaintaining a clear eye diagram and low bit error rate over the above transmission distances.
This is exactly1310nm DFBLaserWidely used5GFronthaul and mid-range single-mode links,and1550nm DFBLaserReasons for its use in long-haul trunk lines and coherent systems——At these two wavelengths,Optical fibers have the lowest dispersion and lowest loss, respectively.。
Windmill DFB laser chip
Hangzhou Wenmi Core Optoelectronics Technology(Windmill Photonics)Professional manufacturing1310nmand1550nmwavelengthDFBlaser chip,Provides butterfly packaging,With narrow line width、High power output、conform toTelcordia GR-468-COREReliability Standards。Suitable for optical modules、Fiber optic sensing、Gas detection and testing instruments and other fields。
Get to know usDFBLaser products →
Common Questions(FAQ)
Are optical modules and optical transceivers the same thing??
Yes。"optical module""optical transceiver""Fiber optic transceiver module"It refers to the same type of device——Module for bidirectional conversion between electrical and optical signals。
Can single-mode optical modules be used on multimode optical fibers??
Technically,Adjust the mode jumper(Mode Conditioning Patch Cable),Single-mode modules can be compatible with multimode optical fibers over extremely short distances.,However, it is not recommended for use in production environments.。in turn,Multimode modules cannot work on single-mode fiber.。The correct approach is to strictly match the module type with the fiber type.。
Why are optical modules commonly used?1310nmand1550nmwavelength?
Because these two wavelengths correspond to the two optimal windows of quartz optical fiber.:1310nmThe dispersion is close to zero.,Suitable for medium-distance transmission；1550nmThe lowest attenuation(about0.2dB/km),Suitable for long-distance transmission。This is determined by the physical properties of optical fibers.。
DFBlasers andFPWhat are the differences between lasers??
FP(Fabri-Perlo)Laser outputs multiple wavelengths,Low cost,Suitable for short distances(about2kmwithin)transmission。DFB(Distributed feedback)Laser outputs a single precise wavelength,extremely narrow spectrum,It can support longer transmission distances.、Higher speed and lower bit error rate。
How long is the lifespan of an optical module??
High-quality optical modules can typically operate for more than1010,000 hours(about11More than 1 year of continuous operation)。Aging of the laser chip is the main influencing factor.,However, under reasonable operating temperature and conditions,The lifespan of optical modules often exceeds the upgrade cycle of the network equipment itself.。
What is"Hot-swap"?
Hot-swap(Hot-pluggable)Refers to the state when the equipment is powered on and running.,The optical module can be directly inserted or removed.,It will not affect the normal operation of the network.。All current mainstream packaging forms(SFP、SFP+、QSFP28、QSFP-DDetc.)All support hot-swapping。
In conclusion
The optical module industry is undergoing rapid transformation.。AIDriven by data center construction800Gand even1.6TOptical module requirements,Silicon photonics technology and co-packaged optics(CPO)The integration method of optical interfaces and switching chips is changing.。
But no matter how the industry changes,One basic fact remains unchanged.:Reliable optical communication,Starting with high-quality light sources。Whether25GThe pre-transmission module or800GData center interconnect module,DFBThe performance of the laser chip directly determines the signal quality.、Transmission distance and final bit error rate。
This is why choosing a reliable laser chip supplier is crucial.——Windmill(Windmill Photonics)exist1310nmand1550nmContinuous in-depth research on two core wavelengthsDFBLaser technology,Providing high-performance optical module manufacturers and system integrators、Highly reliable light source solutions。
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