What is an active optical cable?
Optical modules convert electrical data signals into flashing lasers, which are then transmitted through optical fibers. The optical module has an optical connector for disconnecting the optical fiber from the optical module. Active light glues together the fiber optic connections inside the end of the optical module, creating a complete fiber optic cable assembly, much like a passive fiber optic cable, with a reach capability of only 3-200 meters. The main benefit of active optical cables is that the optical technology has a very wide range of applications, while at the same time working like a simple "plug and play" copper cable.
What are the functions and advantages of active optical cables?
Compared to less expensive passive optical cables, active optical cables offer:
1. The ability to achieve is higher than the 3-7 meter limit of passive optical cable
2, 3 meters – 100 meters multi-mode technology
3. 100-200 meters, with single-mode silicon photonics
4. Lighter weight, thinner fiber optic cable and larger bending radius, which improves airflow cooling efficiency and simplifies system maintenance
Compared to more expensive optical modules, active optical cables provide:
1. Much lower price solution compared to two optical modules and connector-based fiber link
2. Lower power consumption, 2.2 watts, while optical modules (4 channels) are up to 4.5 watts
3. Reduce operating and maintenance costs
How is an active optical cable different from two transceivers with connecting fibers?
Permanently securing fiber is a seemingly simple change that yields a surprisingly large number of technical and cost advantages. Enough to create a whole new category of interconnect products. Because the optical components are contained within the cable, designers do not have to comply with IEEE or IBTA industry standards to achieve transceiver interoperability with other vendors. Therefore, customers can choose the technology with the lowest cost and the best performance. Here are some results that can be achieved with this simple change:
1. The lowest-priced optical interconnects available—almost half the price of optical modules—much more than the cost of missing optical connectors.
2. Plug and Play: Easy-to-use optical cable features – like passive optical cables
3. Long distance: depending on the technology, up to 100 meters and 200 meters
4. Lowest optical power consumption – significantly lower than connected transceivers – saving operating expenses
5. No need to clean and maintain optical connectors – saves operating expenses and improves reliability
6. As with copper passive optical cables, optically isolate the electrical system from the ground loop
How can active optical cables achieve a lower product cost than two transceivers?
Active optical cables use two optical modules with integrated optical fibers. So how much cheaper is it compared to a single optical module with an optical connector?
Cost of testing: Optical testing accounts for 40-60% of the manufacturing cost of an optical module. Active optical cables are tested as electrical tests in switching systems. Fiber optic cable plugged in; test pattern and data run; see results later. On the other hand, optical modules require 500,000 yuan of optical test equipment per site, experienced test engineers, and a lot of time on the test bench. Active optical cables eliminate all these hassles since testing is only in the electrical domain.
Design freedom: Because the optical components are contained within the active optical cable, designers can take advantage of the lowest cost materials and transceiver designs. For example, in addition to removing the four MPO optical connectors (2 on each end), our active optical cables use only one laser, as opposed to four lasers for multimode active optical cables.
How are Active Optical Cables Used in Modern Data Centers?
Although the range of active optical cables can be extended to the limit of the optical technology used (100-200 meters), it is difficult to install a long optical cable of 100 meters long in a crowded data center rack along with expensive optical modules. Usually used between 3 and 30 meters. Only one is allowed per fiber optic cable. Damaged passive optical cables mean replacement because they cannot be repaired. Therefore, active optical cables are usually deployed in open access areas, such as within racks or in open cable trays.
Energy and cost savings have caught the attention of Ethernet hyperscalers and enterprise data center builders, and have since become a popular method of linking top-of-rack switches up to aggregation-layer switches. Several very large companies have publicly stated that they prefer to use active optical cables to connect top-of-rack switches. In addition, single-channel AOC has become very popular in storage subsystems, and some very large builders often run 10G or 25G AOC from top-of-rack switches to subsystems, reaching a passive fiber limit greater than 3-7 Meter.
