2.5G SFP optical module development of high-performance general scheme

1. working principle of the module
Long-range fiber optic sfp module products for unity with APD receiver module, work rate 2500Mbps, transmission distance 80km, electrical interface can hot swap without power, dual LC optical interface plug type, with DDM digital diagnostic functions. Transmitter and receiver module is divided into two parts. LC driven in part by an integrated emission control circuit with APC and DFB-LD components. The integrated circuit receiving LVPECL logic level signal and provide for the LD bias and modulation currents, APC loop current size according to the size of the generated light emitted optical power LD, to achieve automatic control of emitted light power work can be. The integrated circuit with a transmitter shutdown; receiving section includes APD TIA components and limiting amplifier chip. CML limiter amplifier output logic level signal and a signal having a LOS alarm function.

2.5 G electric modulation signal, through TD difference data input feet enter into the light module launch part, through the module within the Laser Driver produces light modulation signal data, through the optical fiber transmission.Optical signal to receive data, through the optical module will receive part of the light signal into electrical signal modulation and shaping amplifier, in through the module of Rx difference data feet output.So as to realize the long- distance transmission of data through the optical fiber.
2. based on SFP-MSA Multi-Source Agreement design
SFP-MSA Multi-Source Agreement sets out our main design SFI 'need to meet the mechanical dimensions, package, module definition and application circuit Goldfinger peripheral module inserted row, making it compatible with a wide range in the optical communication equipment. According to the requirements of the agreement, we have designed single mode fibre sfp housing meets the requirements of the agreement.
3. Based on the design of SFF-8472 standard
SFF-8472 standard defines the main multi mode sfp digital diagnostic functions and modules to achieve the principles of internal software storage space Standard definition, making the system vendors through MOD-DEF modules (0) ~ MOD-DEF (2) of the three legs of the operating parameters of the software control module for real-time monitoring.
According to the definition of this standard, thismulti mode sfp designed to its operating voltage (reported accuracy of ± 3%), operating temperature (reported accuracy of ± 3 ℃), transmitted optical power (reported accuracy of ± 3dB), transmit bias (reported accuracy of ± 10 %), received optical power (reported accuracy of +3 dB) for real-time reporting, enabling the SFP digital diagnostic functions.
4. light-emitting device selection
Because the module work rate reached 2.5G, transmission reach 80km and small packages. So we use the LC 1550nm DFB laser with coaxial isolators as emitting device according to the design. (1) DFB device characteristics: DFB lasers belongs to a single longitudinal mode (SLM, Single LongitudinaL Mode) semiconductor lasers. Compared SLM semiconductor lasers with Fabry-Perot laser, it is no longer independent of the resonant cavity loss pattern, but different vertical mold design paired with different losses.

Design principles and implementation of multi-function monitoring platform SFP optical module

Read by the microcontroller optical modules and CDR-related memory, and in accordance with the parameters that need to be read LCD display real-time, so that the results intuitive and easy to understand. While connected via serial port and external facilitate debugging. In this system, SFP module implemented by CDR I2c bus communication with the microcontroller. fiber optic transceiver module via an external device access signal, the photovoltaic modules into an electrical signal, and then after the clock data recovery CDR, bit error rate, measuring extinction ratio, sensitivity and other parameters with normal test results to see whether the correct comparison. While the optical module is connected via the optical interface with external microcontroller to communicate with the outside world through the serial port for data exchange, each signal via SMA connector leads, as required by coaxial cable to connect the debugger, it is easy to debug.
2.2 optical module monitoring platform software design
2.2.1 software system design structure with a brief description of the microcontroller Atmega128L LCD (Model LM16032) using parallel data transfer, three control bit MCU PA5 ~ 7 and LCD (RS, RW, E) is connected, plus two control LCD display on the Up-key and turn the key down key DownKey and SCM PE5 and PE6 connected to the microcontroller interrupt the way to achieve the appropriate control. SFP microcontroller reads the data from the relevant parameters I2c bus after transmission through parallel to the LCD display. Using the timer mode, so With a frequency greater than 24MHz refresh LCD display.
3 main parameters read
3.1 Temperature parameters read
Because of the module can be used in a high rate of system and has the appearance of small, the layout of the they are usually very compact.In these applications sfp transceiver of rectangular box shape affect the cooling air flow, thus partially weaken the advantages of easy to use, so the temperature inside the module as a useful parameter to measure the long-term stability of the device and device of electro-optic specifications conform to the degree of life.3.2 read voltage parameterIn the SFP working voltage can through sensor installed on the internal PCB circuit for measuring.These measurements can also be used to observe the working voltage drift.And according to the experience can be linked with a given SFP pin or monitoring failure due to the system power supply environment caused by the large voltage fluctuation.
3.3 Read bias current
When reliability prediction has been the most effective transceiver module parameter is the laser bias current, typically used in integrated optical transceiver modules are in constant optical output power mode. Through a closed loop feedback circuit to change the laser bias current so as to stabilize the laser output power. Since the laser efficiency and the threshold values ​​are changed with temperature, and many modules are required to change the laser bias current so as to stabilize the optical output power of the laser, the laser bias current if the variation is not as temperature or voltage changes caused, it shows that the laser potential stability problems.
4 Based on the test platform module parameters
4.1 Bit Error Rate Test
For error test mainly through error instrument, optical module, and the CDR from ring, through error instrument observation error rate is less than 1 hour 10-12.Test procedures and results:(1) good connection test equipment.(2) the work continuously for an hour, once every five minutes record error rate.(3) the bit error rate has been less than 10-12.

Design and Research of Intelligent SFP optical module

Introduction
In the optical communication products, optical module occupies has a very important position. Optical transceiver module as one of the key technologies of optical fiber communication network, is widely used in synchronous optical network SONET) and Synchronous Digital Hierarchy SDH), Asynchronous Transfer Mode (ATM), Fiber Distributed Data Interface (FDDI), as well as Fast Ethernet and thousands Gigabit Ethernet and other systems.
In the present optical communication products, fiber optic transceiver module has been more popular than others, SFP GBIC module module volume ratio reduced by half, but also supports hot-swap capabilities, has been widely used. Meanwhile, in the various existing networks needed optical transceiver module types, more and more requirements are also increasing. To meet the ever increasing performance requirements of the system,Optical module continues to develop intelligent, fast and high-density interconnect direction.
Intelligent SFP optical modules, namely USES the fiber optic sfp module of digital diagnosis function, will become a new generation of optical transceiver module integrated in the window.It can realize network management unit real-time monitoring the temperature of the transceiver module, power supply voltage, bias current, as well as the transmitting and receiving optical power.Through monitoring of these parameters, we can help system administrators predict the life of the light module, fault isolation system and authentication module in the installation of compatibility, etc.
A smart SFP optical module system design
1.1
Transmitting section
The main role of the light-emitting process in the optical transmission module is to convert the optical signal into an electrical pulse signal is a pulse, the electrical signal is input, the output optical signal. Transmitter module, mainly by the laser driving circuit and the TOSA. Which TOSA backlit by the laser diode LD and PD components. LD is used in vertical cavity surface emitting laser VCSEL.
First electrical modulation of the laser drive lasers to meet the input digital fiber optic communications system required drive signal, the drive signal from the bias current Ibias And the modulation current Imod composition, the laser emits an optical signal corresponding to the driving of the driving signal, the optical signal is coupled into the optical fiber and transmitted to the receiving end. In this scenario, the laser driver selection MAX3286.
Laser driver with the functions of automatic power control (APC), APC circuit using the backlight diode in the TOSA, monitoring laser the size of the backlight.When the optical power is less than one rating, through increase the drive current feedback circuit, laser output power increases as the rated power value.Conversely, if the optical power is greater than a certain rating, is through feedback circuit reduce drive current, laser power output is less.APC circuit can dynamically adjust the laser power, therefore, the size of the bias current, can automatically compensate laser due to the change of ambient temperature or aging caused by the change of the output optical power, keep the output optical power range is relatively stable.
1.2
Receiving part
The main role of the receiver module is attenuated after
deformation weak optical fiber cable transmission signal to a pulse electric pulse signal by photoelectric conversion, and give sufficient amplification, a standard reduction of the digital pulse signal. Optical receiver module schematic shown mainly by the photodiode PD, a preamplifier, a limiting amplifier and other components. Which photodiode and preamp integrated package together constitute ROSA.
A photodiode is a core device of a digital optical receiver, an optical pulse signal will be the electrical pulse signal by photoelectric conversion, commonly used are PIN photodiodes and avalanche photodiode APD. Optical signal from the optical interface enters the photodiode PD, is converted into a weak current, the current through the pre-amplifier and converted into a voltage level is amplified to an appropriate level.
Effect limiting amplifier output of the preamplifier is the magnitude of different amplitude analog signal into a digital signal, these signals can be amplified. To photoelectric detectors with a good match and get the low-noise and wide-band preamplifier gain is not too high, the preamplifier output voltage amplitude is usually from a few millivolts to tens of millivolts, such small signals can not be directly output optical module is therefore necessary to further enlarge the signal; the other hand, the photodetector detects the light signal from the amplitude of the current signal in a defined tolerance level, the tolerance limits of the capacity of the fiber considered Poor, splice loss and the parameter fluctuations caused by temperature and aging, however, the data for further processing, the signal amplitude is preferably a constant value.
Therefore, limiting amplifier requires a certain dynamic range, which usually requires a dynamic range of more than 20dB.
1.3
Digital Diagnostics DDM part
Digital diagnostics mainly composed of MCU to complete. By temperature MCU, the network management unit may receive real-time monitoring module, the power supply voltage, laser bias current and the light emitting and receiving power. By measuring these parameters, the management unit can quickly identify the specific location of fiber link failure occurs, simplify maintenance, improve system reliability.
Five DDM parameter acquisition circuit for acquisition by the first conversion, the inputs to the ADC, ADC five circuit analog voltage into a digital signal sent by the decoder circuit is stored in a memory support DDM corresponding address bit . Transmission of information via a two-wire serial interface (SCL clock line and data line SDA) to achieve.

PCB simulation design of Gigabit SFP optical transceiver high-speed circuit

High-speed digital circuit design means that if the rise time of the signal propagation delay times of less than 4, PCB.The signal on the board can present transmission line effect, such a design is called high speed digital circuit design.And the Series digital circuit design method is different, high speed digital design need SI simulation analysis.SI simulation analysis generally divided into before wiring two process simulation and post layout simulation, its main task is found in the system design process and improving the sI problems, ensure the quality of signal transmission functions and the right time, is to ensure that the key step in the design is successful.

Gigabit SFP optical signal transceiver card is mainly composed of four modules: (SFP) fiber optic transceiver module, the large capacity data cache (SDRAM) (PCI9656), PCI bus interface module, control module (FPGA).Implementation of main function is to be able to send and receive gigabit Ethernet optical signals, on the physical layer and data link layer handling gigabit Ethernet protocol, IP packets and through PCI bus is extracted in the computer's memory.Demand support vet2 PCI card. Agreement support DMA transfer mode, data transfer rate is not less than 125 MB/s.

Light module in the design of input and output electric signal frequency up to 1.25 Gbps, using the LVPECL difference signal, the gigabit difference signal simulation discussed in literature [3].First of all, establish simulation model as shown in figure 7.Single line impedance 50 1000 f2 differential impedance (X1), signal rate of 1.25 GHz.Outl LVPECL difference output IBIS model for sfp transceiver module, Inl for FPGA LVPECL differential input IBIS model.

Design by using based on SI simulation analysis and design of high-speed signal PCB wiring rules, solved the gigabit sfp ports signals in the process of sending and receiving card design, signal integrity problems of cloth plate a successful, completely meet the requirement of design index, and avoid the repeat design from the signal integrity issues.In the process of high speed digital circuit design, based on SI simulation analysis early in the design of the product as much as possible to solve the signal integrity problems, so as to minimize the product cost, shorten the development cycle.

Data communication with intelligent CSFP optoelectronic integrated optical modules

In recent years, along with fiber to the home , all-optical network applications , such as the rise of hot spots , the communications industry is facing a double challenge of bandwidth and speed , high-capacity , high-speed and high-quality optical fiber communication has become an inevitable trend of development of information industry . Optical transceiver module is an important part of the construction of optical networks , its core function is to provide optical transmission network between the various interfaces, optical or electro-optical conversion is completed , make sure to connect communication network . Currently wider application of miniaturized optical module types are hot-pluggable (SFP) module series. In the current mainstream of communication capacity and rate, which can satisfy the requirements of communication . But with the rise of a series of hot applications and low-cost optical modules , and further demand for high -capacity links , miniaturized compact hot-pluggable (CSFP) optical transceiver modules have come into being . In the now popular SFP on the basis of industrial packaging , through the use of dual or even quad-channel design , CSFP does not change the existing interface form, but will be reduced dimensions to the existing standard 1/ 2 or 1 /4 , also through a combination of The number of channels can be flexibly configured . Use of highly integrated optoelectronic circuits and packaging technology developed CSFP fiber optic transceiver module inherits all of the technical advantages , greatly reducing the optical modules and communication systems equipment dimensions, exponentially enhance information throughput and port density while also reducing the system cost , a huge commercial value . This paper aims to study and design of an integrated two traditional Bidirectional bidi sfp transceiver for CSFP , and its performance test results through further analysis of the data , verify product performance, demonstrated the feasibility of the design, for the CSFP the actual production of optical modules provide a theoretical basis
CSFP in the traditional optical module sfp transceiver module dimensions, integrates two BIDI SFP modules. The module consists of two PLC BOSA to achieve two-way transceiver under the original two channels of the same dimensions . Pin to define and monitor the amount of conventional SFP modules are quite different , the other basic functions , like the structure shown in Figure 3 , where the LOS alarm signals , IC chip is integrated , MCU for the microcontroller , EEPROM is electrically EEPROM , BOSA optical transceiver module .
CSFP completed the functions of the two traditional single fiber bidirectional SFP module integration , the structure contains two independent optical transmitting and receiving channels, each channel consists of a PLC BOSA device is responsible for the completion of the optical signal receiving and transmitting signals , is CSFP core component module .
BOSA emitting portion of the transmitter and the triple chip driver circuit, and is mainly composed of a laser diode transmitter (LD) and the monitor light emitting diode backlight power (PD) components. The effect is to provide a driving circuit required laser bias and modulation currents , the former is used to turn the laser operation, the latter is used to load the received modulated electrical signal to the output optical signal. The current drive circuit generally have automatic power control (APC) function, you can ensure that the whole laser light power is constant, the principle is based on the current size of the monitor diode backlight dynamically adjust the bias current.
Micro controller main block to the laser driver circuit, main amplifier, and EEPROM control.EEPROM basic unit is mainly used for storage of product model, series number, production date, such as fixed information related products, and CSFP module of digital diagnostic monitoring (DDM) should be added to the transfer of acquisition signal circuit.These circuits for module output optical power, the input optical power, working voltage, temperature and bias current parameters such as real-time monitoring and reporting.Acquisition circuit these parameters corresponding to the instantaneous voltage values to transform circuit, the output of digital signal block is stored in the EEPROM of the corresponding unit.
CSFP system interface between the modules and the upper machine adopts the I2C bus method, namely the clock line (SCL) and a data line (SDA), achieved by gold finger electric interface, complete PC optical module information, speaking, reading and writing.The data transmission between MCU and block storage device EEPROM is through the SPI bus, namely the clock line, data input and data output line.MCU through the I2C bus to monitor two way passage, once detected a channel abnormal changes of main parameters of MCU respectively to TX1 - Fault or TX2 - Fault, said error channel 1 or 2.MCU TX1 - Fault and TX2 - Fault output pins at the same time input terminal connected to an or gate, only when the two way passage all work, module goldfinger TX - don't Fault pin up a machine alarm.The abnormal, otherwise, all the way to transport channel signals alarm module.

Cost factors restricting the development of 10GbE Ethernet

Of course, we will be told that this year will be the year 10Gb / s Ethernet great development over the past few years as we have been repeatedly told that. The reason is not because of technical ability -? 10 gigabit ethernet sfp has stabilized for some time - but because of the cost.
When 1000 base-t technology dominate the market, you can take 10/100 of your device is inserted into the 10/100/1000 switch, and then it can work.More important, 1 gb/SEC Ethernet port on a switch cost has dropped to very low, so that if we don't need to maintain high throughput on these links, we all feel that they spend money on port.If we need 1 gb/SEC Ethernet is there, even if we don't need most of the time.
Some people believe that 10 gb/SEC Ethernet will follow the same pattern, but even the optimists are also beginning to forecast by 10 gbase - 2014 T to be made more than the alternative solution deployment.Even if by that time, we are still going to deal with the various types of 10 gbe interface type.The price is still an obstacle.The price of each switch port 1000 base-t can only $10, but the most common type of 10GBASE SFP+ - the switch port cost is 300 dollars, I expect this costs can drop to below $200 by the end of the year.10 gbase - T still more expensive than the unit switch port costs of SFP +, and compared with the SFP +, 10 gbase - T more rare on the market.
Cisco will tell you the opportunity 10Gbase-T is now. Of course, it must rely on something like "unit Gb costs" kind of lying in order to convince people. Most companies are not prepared to increase the bandwidth of the connection, so just imagine that we will do it only shows trying to sell 10GbE vendors completely unwilling to participate in the 10GbE market commercialization in the past.
Clever powerpoint slides can talk "10 times more bandwidth, only three times the cost", but it is only used in the mainstream of avoiding real problem: most businesses don't need to be 10 times the bandwidth, and is not willing to pay 3 times the cost.
If you are switching infrastructure is Cisco end - to - end , you may not care about how cost . You may not care about the SFP + $ 100 or $ 300 straight cable 's 1000base-sx sfp transceiver module . If your business depends on commodity SME switches, then you - like me - would have been free to use almost 1Gb / s link , 10GbE down until a reasonable price level.
Cisco , Juniper and other vendors are not prepared to promote commercialization. They have been marginalized in the face of market problems in 2013 . Software-defined networking is increasingly becoming a threat , eventually it will be possible crowding out of our core infrastructure for decades with these vendors of proprietary products.
Intel has vigorously to 10 gbe configuration to the motherboard and promote its commercialization.All servers in the future will be ready to use 10 gbe, but for many companies, they will be no one to dialogue.
As a giant switch chip, Intel can choose tomorrow, let 10Gbase-T Explosive appear on the market within a quarter. The company produces excellent 10GbE switch chip - with a very low price to D-Link or Netgear will rewrite the pattern of the entire market.

The industry's first quad-channel SFP interface for conformance testing and debugging solutions

Oscilloscope market makers announced that launched the first in the industry for four-channel SFP interfaces (QSFP +) compatible product consistency test and debug the solution.New QSFP + solution based on the liner the DPO/DSA/MSO70000 oscilloscope, including to design, test and verify the QSFP + design requires all the components, HCB fixture and the test automation and software debugging tools.
QSFP + is a compact for data communication applications can heat change the transceiver.It will network equipment main board (such as switches, routers, media converter and similar devices of the motherboard) through the interface connected to the cable.SFF committee released the latest specification of the data transmission rate reaches 4 x10gb/s and support serial connection SCSI, 40 g Ethernet, Infiniband 20 g / 40 g and other communication standards.Compared with the 10GBASE SFP+ Transceiver, QSFP + module port density increased by 3-4 times."
QSFP + evolve and sfp transceiver module, this means that engineers need comprehensive testing solutions to efficient and rapid verify its design and put them to the market", the company general manager of high-performance oscilloscope Brian Reich said, "our solutions to provide automatic conformance testing function, compared with manual test time can help customers to save as much as 80%, at the same time provide to our world-class seamless migration of debugging environment."
Unlike the other based on a sampling oscilloscope sfp plus transceiver test solutions, the new Tektronix SFP + QSFP + Tx solution is based on real-time oscilloscope, which is engaged in the preferred platform for QSFP + and SFF-8431 and SFF-8635 product design engineers. SFP + QSFP + Tx solution also provides support for Transmitter Waveform Distortion Penalty for Copper (TWDPc) test (SFF- 8431 standard requirements for this test), which is currently unique.
SFP + QSFP + Tx solution using a simple menu driven measurement Settings and provide one-click conformance testing, and automatic report generation "pass/fail", help to improve the efficiency of test and measurement.In addition to the standard consistency requirements, this solution also support the design verification, and configuration of the test, such as window and other parameters of flexible control.If the design of the conformance test failure, the user can use DPOJET (jitter) and timing analysis Settings file to reduce debugging time.