The sharp increase in demand for video optical transceivers has brought new demands for fiber bandwidth capacity and device management. In order to meet the requirements of this change, there are more and more types of optical transceiver modules as one of the core devices, and the requirements are getting higher and higher, and the complexity is also developing at an alarming rate. However, as far as the overall trend is concerned, optical modules are moving toward miniaturization, low power consumption, high speed, long distance, hot swap, and intelligence.
High rate
The continuous expansion of the security market and the difficulty in fiber construction have made the system more and more efficient for the transmission of single fiber of optical transceivers, so ultra-high-speed optical modules have been gradually used on optical transceivers. The higher the transmission rate and the larger the capacity, the lower the cost of transmitting each video. Now 2.5G and CWDM optical modules have been stably applied to video optical transceivers. Modules with higher 4G, 8G and 10G are also mature. At present, SDH single-channel optical systems are impacting 40Gbit/s. From the current circuit technology, 40Gbit/s is close to the limit of “electronic bottleneck”. The rate is higher, the signal loss, power dissipation, electromagnetic radiation (interference) and impedance matching are difficult to solve, and the current price is too high. The video optical transceiver has not yet mature application, and the cost is decreasing and supporting. The maturity of the IC program is believed to be applied soon.
miniaturization
With the popularization of optical fibers, the global optical communication market is moving toward the all-optical network, and the number of optical communication devices is increasing, so the volume requirements for devices are becoming smaller and smaller. The interface board contains more and more interfaces, which further aggravates the density of the device. In order to meet the requirements of the communication device for the optical device, the optical module is developing into a highly integrated small package. The interface of the optical module has evolved from ST and FC to SC and smaller LC and MT-RJ type connectors. The package form of the corresponding optical transceiver module has also evolved from plastic packaging to metal packaging. The pin arrangement and package are developed from a single row of 9 feet, a double row of 5 feet or 10 feet to the direction of the gold finger. The SFF (Small Form Factor) small package optical module adopts advanced precision optics and circuit integration technology. It is half the size of the ordinary duplex SC (1X9) type optical transceiver module, and can double the number of optical ports in the same space. Increase line port density and reduce system cost per port. And because the SFF small package module uses a MT-RJ interface similar to the copper network, the size is the same as the common computer network copper interface, which is beneficial to the transition of the existing copper-based network equipment to a higher-speed optical network. To meet the rapid growth of network bandwidth requirements, in some applications, some optical transceiver manufacturers have used SFF, SFP modules, and manufacturers use a single-row 9-pin module and pigtail LC interface to achieve miniaturization. The smaller the size of the communication device brings about a problem of heat dissipation, which requires that the photovoltaic device be developed in the direction of low power consumption. The current small package (SFF, SFP) optical modules have all been powered by low voltage 3.3v, which ensures the normal operation of the system equipment.
Hot swap
Future optical modules all support hot-swap capability, which means that the module can be connected or disconnected from the device without powering down. Because optical modules are hot-swappable, network administrators can replace or expand without shutting down the network, which will not affect the continuous operation of the system. This greatly reduces the cost of maintenance and upgrades, enabling end users to better. Manage their devices. The optical modules that support this hot swap currently have GBIC and SFP optical modules. Due to its small size, the SFP can be directly plugged into the board and has a wide range of applications.
Long distance
Another development direction of optical modules is long distance. China's vast territory, coupled with the increasing application range of optical transceivers, makes the transmission distance requirements higher and higher. If optical modules of FP type and 1310nm wavelength lasers are used, the 8-channel video optical transceivers in the typical G652 fiber system are The transmission distance can also reach more than 20km, and the transmission distance of the optical transceiver of 1 or 2 channels can reach more than 40km. If a DFB type, 1550 nm wavelength laser is used, the 8-channel video optical transceiver can also achieve 80 km transmission, of course, the price is also much more expensive. It is worth mentioning that in order to save fiber resources, many optical transceivers now use single-fiber bidirectional transmission. Single-fiber bidirectional modules are also used on optical modules. The forward and reverse transmissions are paired with 1310nm and 1550nm lasers. In terms of cost, FP type lasers are generally used. At this time, it should be noted that the 1550 nm wavelength light has a more serious dispersion characteristic in the optical fiber, so its transmission distance is limited, and generally only at a low rate. 40km, if you need to transmit a long distance, you should use a DFB type laser.
Intelligent
The SFP (short for Small Form Pluggable, which is a miniaturized package hot-swappable module) module can be simply understood as an upgraded version of GBIC. However, the SFP module is half the size of the GBIC module and can be configured with more than double the number of ports on the same panel. It is an SFP intelligent optical module with digital diagnostic function. The intelligentization of optical modules is reflected in two aspects.
The first is that the built-in IC of the optical module has parameters such as monitoring the temperature of the optical module, the power supply voltage, the laser bias current, and the transmit and receive optical power. The implementation of these five parameters is converted into digital quantities by the analog-to-digital conversion circuit inside the module, except for the acquisition and conversion circuits, and is provided to the user in binary form. Through these parameters, the working state of the optical transceiver can be monitored.
The second means that the optical module has a digital diagnostic function. The digital diagnostics and details of the SFF-8472 are specified in the SFF-8472 MSA. SFF-8472 retains the address mapping of the original SFP/GBIC at address A0h, and adds a new 256-byte memory location at address A2h. In addition to providing parameter detection information, this storage unit defines alarm flags or alarm conditions and status mirroring of each pin. According to the specification, the parameter signals are detected and digitized on the circuit board inside the module. The calibrated results are then provided or digitized measurements and calibration parameters are provided. The monitored information is stored in a standard memory structure and read through a dual cable serial interface. The digital diagnostics function in the optical module provides a performance monitoring method for the system to help the system manage the life of the optical module, locate and isolate system faults. The fault isolation feature allows the system administrator to quickly locate the location of the link failure, either in the module or on the line, on the local module or on the remote module. By quickly locating faults, the system's fault repair time is reduced.
In addition, in order to match the hot plugging characteristics of the optical module, the intelligent module also reserves a certain storage unit. Customers can write passwords or protocols in the storage unit to restrict unauthorised replacement of SFP modules, thus ensuring the intellectual property and customer benefits of the manufacturer.
Because SFP modules are easy to interchange, optoelectronic or fiber optic networks are easier to upgrade and maintain than traditional soldering modules. Instead of replacing the entire board containing multiple soldering modules, it can be removed or replaced with a single module to repair or upgrade. This can greatly reduce the cost of maintenance and upgrades. And SFP has many advantages: (1) high performance, outstanding mechanical and optoelectronic characteristics, and user-friendly; (2) long interconnection distance, support 1000Base-LH standard, the longest distance can be achieved when using single mode fiber 70km; (3) A variety of optical fibers can be connected, in addition to SFP supporting 1000Base-LH standard, and SFP supporting 1000Base-SX and 1000Base-LX standards.
Although on the current video optical transceiver, the single-row 9-pin module occupies most of the applications. However, in terms of the development trend of the module, the SFP optical module with the above advantages has gradually become the mainstream optical module. Future hotspots of optical components are mainly concentrated in three large blocks, wide area network, access (PON) networks and LAN/SAN network markets. Active devices based on MSA modules and PON networks will be a very popular market, along with The rapid growth of metro access and data communication, and the emergence of SFP optical modules meet the needs of the subsequent development of video optical transceivers. Like the growing communication system, the intelligent SFP module technology represents the development trend of the new generation of optical modules. The cornerstone of a generation of high-speed optical modules.
