1. Overview of WDM Integrated Devices
WDM (Wavelength Division Multiplexing) integrated devices, as a key technology in modern optical fiber communication, utilize WDM technology to enable simultaneous transmission of multiple wavelengths of light signals over a single fiber, significantly increasing the total data transmission bandwidth.
WDM technology was first developed in the 1990s, with the initial commercial WDM systems supporting 8 channels, each with a bandwidth of 2.5Gbps. With continuous advancements, by 2001, products on the market supported up to 96 channels, each with a bandwidth of 10Gbps, achieving a total bandwidth of 960Gbps. Today, WDM integrated devices continue to evolve, with improved transmission capacity and efficiency.
WDM integrated devices are particularly suited for high-bandwidth applications such as data center interconnection, metropolitan area networks, and long-distance fiber optic communication links. For example, in data center interconnect (DCI) scenarios, the OTN3100 integrated WDM device, only 1RU in size, supports up to 1.6T (16*100G) transmission capacity and can be smoothly expanded to 3.2T per fiber through device stacking. This equipment employs high-density optical-electrical integration technology, avoiding complex patch cord connections, and easily forms an end-to-end complete WDM transmission solution, providing an exceptional user experience for DCI transport networks within metropolitan areas.
The working principle of WDM integrated devices is based on wavelength division multiplexing. At the transmission end, a multiplexer combines multiple signals from different light sources into one signal, with each light source emitting a unique wavelength. The combined signal is then transmitted through a single fiber. At the receiving end, a demultiplexer separates the composite light signal back into the original multiple signals, which are then further processed by an optical receiver to restore the original signals.
In summary, WDM integrated devices, with their high bandwidth capacity, flexibility, and scalability, play an increasingly vital role in modern communication.
2. Types and Characteristics of WDM Integrated Devices
(a) Differences between CWDM and DWDM
CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) differ in several aspects:
– Channel Spacing: CWDM devices have wider channel spacing of 20nm, allowing transmission of 18 wavelengths within the 1270nm to 1610nm spectral range. In contrast, DWDM devices feature narrower channel spacings, such as 0.2nm, 0.4nm, 0.8nm, or 1.6nm, and can support 40, 80, or even 160 wavelengths.
– Transmission Distance: Due to the high wavelength density in DWDM devices, they can transmit over longer distances than CWDM devices. For example, a 10G SFP+ CWDM module can reach up to 100km, while a 10G SFP+ DWDM module can also reach 100km; however, in practical applications, DWDM is typically used for longer distances.
– Laser Modulation: CWDM generally employs non-cooled lasers, while DWDM requires cooled lasers to ensure better performance, higher safety, and extended lifespan.
– Cost: CWDM devices are generally more cost-effective than DWDM due to the use of non-cooled, electronically tuned lasers in CWDM, which lowers the cost compared to the thermally tuned cooled lasers required for DWDM.
(b) Choosing Between Active and Passive WDM**
Active and passive WDM multiplexers have distinct characteristics and are suited for different scenarios.
– Wavelength Channels: Active WDM multiplexers support more wavelength channels, thus providing higher bandwidth and better fiber utilization. Passive WDM multiplexers support fewer wavelength channels.
– Management: Active WDM multiplexers are easier to manage, allowing for online wavelength adjustments, making expansion simpler. Passive WDM multiplexers can increase management complexity when network expansion is needed.
– Transmission Distance: Active WDM multiplexers are suitable for long-distance transmission, whereas passive WDM transmission distance is limited by the power of the optical module.
– Cost: Passive WDM multiplexers do not require optical amplifiers or dispersion compensators, making network deployment costs lower. In contrast, active WDM multiplexers involve higher deployment costs, as well as more complex management and maintenance.
In summary, passive WDM multiplexers may be more suitable for simpler network structures, fewer sites, lighter traffic, no network management requirements, and lower budgets. Conversely, for complex networks, with multiple sites, heavier traffic, network management requirements, and higher budgets, active WDM multiplexers are likely the better choice.
