Things We Should Know About SFP Transceiver

In today’s data center, fast Ethernet is out of date.  What takes the place of it is SFP transceiver. Although SFP transceiver is commonly applied in the data center, and there are still many people knowing little of it, such as SFP transceiver types, SFP applications, SFP use tips and so on. Now this article will introduce things we should know about it there.

What Is SFP Transceiver?

The small form-factor pluggable (SFP) is a compact, hot-pluggable optical module transceiver used for both telecommunication and data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. It is a popular industry format jointly developed and supported by many network component vendors.

SFP Transceiver

An SFP interface on networking hardware provides the device with a modular interface that the user can easily adapt to various fiber optic and copper networking standards. Existing SFP transceivers support SONET, gigabit Ethernet, Fibre Channel, and other communications standards. Due to its smaller size, the SFP has replaced the gigabit interface converter (GBIC) in most applications; the SFP is sometimes referred to as a Mini-GBIC. In fact, no device with this name has ever been officially defined in the MSAs.

Types of SFP Transceiver

SFP transceivers are available with a variety of transmitter and receiver specifications, allowing users to select the appropriate transceiver for each link to provide the required optical reach over the available optical fiber type. With the respect to SFP transceiver types, it can be sorted out according to transmission rate, wavelength. The introductions of them are as below:

Classified according to the SFP transceiver rate, it includes 155M/622M/1.25G/2.125G/4.25G/8G/10G, in which 155M and 1.25G are usually applied. Besides, 10G tech is maturely developed, and the demands for it tend to rise.

Sorted according to the SFP wavelength, it consists of 850nm/1310nm/1550nm/1490nm/1530nm/1610nm, in which 850nm wavelength belongs to multimode, and its transmission distance is less than 2KM; 1310nm/1550nm wavelength belongs to single mode, and the transmission distance is over 2KM. Relatively speaking, the prices of 850nm, 1310nm and 1550nm wavelength are lower than the other three types. Moreover, bare optical modules without signs are easy to get mixed up, thus manufacturers usually make a clarification in the colours of pull rings. For example, pull rings of  modules differ in colors, which means they distinguish in wavelengths. Black represents 850mn wavelength; blue represents 1310mn wavelength; yellow represents 1550mn wavelength; and purple represents 1490mn.

In addition, it can also be divided into these categories, such as Gigabit Ethernet SFP, Fast Ethernet SFP, BiDi SFP, CWDM SFP, DWDM SFP, Fiber Channel SFP and so on, in which Gigabit Ethernet SFP and CWDM SFP are relatively common ones (Gigalight will provide several ones for reference at the end of this article, shown as the tables)

Applications

SFP sockets are found in Ethernet switches, routers, firewalls and network interface cards. Storage interface cards, also called HBAs or Fibre Channel storage switches, also make use of these modules, supporting different speeds such as 2Gb, 4Gb, and 8Gb. Because of their low cost, low profile, and ability to provide a connection to different types of optical fiber, SFP provides such equipment with enhanced flexibility.

Use Tips

If module is improperly operated when used, it may not work. Once this situation happens, things that should be done first is to check it carefully and analyze the causes. The failure of optical transceiver usually includes these two types: the failure of transmitting terminal and receiving terminal. The commonly-seen reasons of failure are as below:

1.    The contaminated interface of fiber connector result in the secondary contamination of optic module’s optical port

2.    Optical port of optic module is exposed to the air, and dust into it brings about contamination.

3.    Optic fiber connector is with bad quality.

Conclusion

Although the needs for higher rate products will be increased with the development of tech, and SFP transceiver will still be in the optic market for a long time due to its advantages in miniaturization, port density and so on. This article have a relative comprehensive introductions to SFP transceiver, and it’s believed that it will be beneficial to us in the future use of SFP transceiver.

More Information :

1.    Gigalight Gigabit Ethernet SFP:

Gigalight Gigabit Ethernet SFP	Part Number	Description
1000BASE-T SFP	GE-GB-P3RT-E	Compliant with the Gigabit Ethernet and 1000BASE-T standards as specified in IEEE 802. 3-2002 and IEEE 802.3ab, which supporting 1000Mbps data- rate up to 100 meters reach over unshielded twisted-pair category 5 cable.
1000BASE-SX SFP	GP-8524-S5TD	Supporting data-rate of 1.25Gbps and 550m transmission distance with MMF. All modules satisfy class I laser safety  requirements.
1000BASE-EX SFP	GP-3124-L4TD	Supporting data-rate of 1.25Gbps he transceiver consists of three sections: a DFB laser transmitter, a PIN photodiode integrated with a and 40km transmission distance with SMF
1000BASE-ZX SFP	GP-5524-L8TD	Supporting data-rate of 1.25Gbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.

2.    Gigalight CWDM SFP Transceivers:

Gigalight CWDM SFP Transceivers	Part Number	Description
CWDM-SFP-1490nm	GPC-4903-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1510nm	GPC-5103-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1530nm	GPC-5303-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1550nm	GPC-5503-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1570nm	GPC-5703-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1590nm	GPC-5903-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.
CWDM-SFP-1610nm	GPC-6103-08TD	Supporting data-rate of 155Mbps and 80km transmission distance with SMF. Compatible with SFP Multi-Source Agreement (MSA) and SFF-8472.

Note: Infiberone is the online store of Gigalight

CWDM vs. DWDM：What Are the Differences？

It’s known that WDM(Wavelength Division Multiplexing) is divided into DWDM(Dense Wavelength Division Multiplexing) and CWDM(Coarse Wavelength Division Multiplexing). With respect to these two types, there is no doubt that DWDM(Dense Wavelength Division Multiplexing) is the first choice in the fiber applications field. However, due to its high price, manufacturers who are lack of finances are hesitant to purchase it. At this time, most of them prefer to choose CWDM with lower cost. As for difference between DWDM and CWDM, it’s far more than this. Today, this article will make an introduction in a way of CWDM vs. DWDM by Gigalight.

1.    What Is CWDM ？

CWDM is a wavelength multiplexing technology for city and access networks. Transmission is realized using 18 channels with wavelengths between 1270 nm and 1610 nm. Due to the channel spacing of 20 nm cost-effective lasers can be used. The channel width itself is 13 nm. The remaining 7 nm is designed to secure the space to the next channel. Moreover, CWDM is very simple in terms of network design, implementation, and operation. CWDM works with few parameters that need optimization by the user.

CWDM highlights

l  Up to 18 CWDM wavelength over one pair of fiber

l  CWDM channel spacing 20 nm, 1270 nm to 1610 nm

l  Distances up to 120 km

l  Cost-effective WDM solution

l  Scalable by hybrid CWDM/DWDM - perfect solution for your investment

 2.    What Is DWDM ？

DWDM is a technology that puts data from different sources together on an optical fiber, used in fiber optics to increase bandwidth over existing fiber optic backbones, and is with each signal carried at the same time on its own separate light wavelength. The “dense” here means that the wavelength channels are very close to each other.        Besides, DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber. DWDM systems require complex calculations of balance of power per channel, which is further complicated when channels are added and removed or when it is used in DWDM networks ring, especially when systems incorporate optical amplifiers.

DWDM highlights

l  Up to 96 DWDM wavelength over one pair of fiber

l  DWDM channel spacing 0.8 nm (100 GHz grid) or 0.4 nm (50 GHz grid)

l  Distances over 1,000 km can be achieved with the use of optical amplifier

l  DWDM wavelength: 1528 nm (channel 61) to 1563 nm (channel 17)

Seen from the brief  introductions of CWDM and DWDM, they distinguish in wavelength spacing, transmission distance. Well, actually, they also  differ in cost, optic modulation, power requirements and so on. The following content will be involved in CWDM and DWDM comparison from perspectives of wavelength spacing, transmission distance, cost, optic modulation, power requirements one by one.

CWDM vs. DWDM

3.    CWDM vs. DWDM: Which One Is Better? 

In wavelength spacing, CWDM supports up to 18 wavelength channels transmitted through a fiber at the same time. To achieve this, the different wavelengths of each channel are 20nm apart. DWDM, supports up to 80 simultaneous wavelength channels, with each of the channels only 0.8nm apart. CWDM technology offers a convenient and cost-efficient solution for shorter distances of up to 70 kilometers. For distances between 40 and 70 kilometers, CWDM tends to be limited to supporting eight channels. Unlike CWDM, DWDM connections can be amplified and can therefore be used for transmitting data much longer distances.

In transmission distance, DWDM is available for a longer distance transmission by keeping the wavelengths tightly packed. It can transmit more datum over a larger run of cable with less interference than CWDM system. CWDM system cannot transmit data over long distance as the wavelengths are not amplified. Usually, CWDM can transmit data up to 100 miles (160km).

In cost, the DWDM cost is higher than CWDM cost. Due to the uneven distribution of temperature in wide optical wavelength range, and temperature is hard to be tuned, which results in the high cost. While CWDM can make it so that the cost of CWDM is reduced in a large scale, which is now 30% of DWDM cost.

In optic modulation, they are different from each other. The optic modulation of CWDM adopts the electronic tuning instead of non-cooled laser. However, on the contrary, the optic modulation of DWDM adopts the cooled laser and utilizes the temperature for tuning.

In the power requirements, DWDM has significantly higher power requirements than CWDM. For example, DWDM lasers are temperature-stabilized with peltier coolers integrated into their module package. The cooler  with associated monitor and control circuitry consumes around 4W per wavelength. Meanwhile, an uncooled CWDM laser transmitter uses about 0.5W of power.

4.    Conclusion

By the CWDM and DWDM comparison, the difference between CWDM and DWDM is apparent. Although they respectively have their own unique advantages, and it seems that CWDM will be more attractive for carriers who need to upgrade their networks to accommodate current or future traffic needs while minimizing the use of valuable fiber strands, on account that CWDM’s ability to accommodate Ethernet on a single fiber enables converged circuit networks at the edge, and at high demand access sites. Of course, if out of consideration of bandwidth and transmission distance, DWDM is also a good choice. In a word, it’s up to one’s specific demands.

Things You Should Know about QSFP-DD

To further satisfy the market demands for high speed, high density networking solutions, QSFP-DD ( double density QSFP) come into sight of people, which is a new module developed by the QSFP-DD MSA as a key part of the industry’s effort to enable high-speed solutions. It’s known that there are still many people unfamiliar with it on account that its advent is for a short time. Then in this article, things you should know about QSFP-DD will be introduced by Gigalight.

What’s QSFP-DD?
QSFP-DD means Quad Small Form Factor Pluggable Double Density, in which the “Double Density” refers to the doubling of the number of high-speed electrical interfaces that the module supports compared with a common QSFP28 module. QSFP-DD is not only a new module but also cage/connector system similar to current QSFP, but with an additional row of contacts providing for an eight lane electrical interface, which can expand the standard QSFP four-lane interface. Furthermore, QSFP-DD is able to operate up to 25Gbps with Non-Return-to-Zero (NRZ) modulation or 50Gbps with Pulse Amplitude Modulation (PAM4). After that, QSFP-DD form factor is allowed to address solutions up to 400Gbps per QSFP-DD port, while providing backward compatibility with 40Gbps and 100Gbps.


An Introduction to QSFP-DD Specification
What characteristics QSFP DD has are defined by QSFP-DD specification with broad market support, which is released by the QSFP-DD MSA group and overcomes the technical challenges of specifying a QSFP28 compatible double-density interface. The QSFP-DD specification defines a new pluggable form factor that supports 8 high speed electrical interfaces connecting to the host. This will include a mechanical module, a single height 1×1 surface mount cage and connector and a press fit 2×1 cage with integrated connector, thermal, pinout and management specifications. The QSFP-DD can support both optical and copper interfaces, but those physical layer specifications will be defined outside of the MSA specification as is usual for form factor MSA specifications.
Simultaneously, the QSFP-DD specification also defines a module and both a stacked height integrated cage/connector system and a single height cage/connector system. These expand on the QSFP form factor, the industry’s leading multi-lane pluggable form factor used across Ethernet, Fibre Channel and InfiniBand for 40Gbps and 100Gbps network applications.

What’s the QSFP-DD Merits and Features?
QSFP-DD pluggable modules under the definition of QSFP-DD specification, can quadruple the bandwidth of networking equipment to keep pace with advances in ASIC technology. By quadrupling aggregate switch bandwidth while maintaining port density, QSFP-DD will support continuing growth in network bandwidth demand and datacenter traffic. Systems designed for QSFP-DD modules will be backward compatible with existing QSFP form factors and provide maximum flexibility for end users, network platform designers and integrators.
Except for these merits, QSFP-DD is also with those unique features:

• Expanding on the QSFP pluggable form factor, a widely adopted four-lane electrical interface
• 2×1 stacked integrated cage/connector
• SMT connector and 1xN cage
• Cage design optimizations and module case optimizations enable thermal support of at least 12w per module
• QSFP-DD electrical interfaces will employ eight lanes that operate up to 25Gbps NRZ modulation or 50Gbps PAM4 modulation, providing solutions up to 200Gbps or 400Gbps aggregate
• QSFP-DD can enable up to 14.4Tbps aggregate bandwidth in a single switch slot

Conclusion
QSFP-DD, available for 200G/400G Ethernet, is a good choice to meet the industry need for high-density, high-speed networking solutions from any perspective. It is predicted that QSFP-DD will become an useful family of modules for the industry with applications at 400GbE and beyond. Meanwhile,  there are no efforts underway to define these new speeds but it is expected that QSFP-DD will evolve to support higher data rates for future applications. In addition, to keep pace with the market development trend, Gigalight launches 200G QSFP-DD, providing reliable long life, high performance, consistent service and so on, based on advantages of QSFP-DD.

How Much Do You Know about CWDM?

As is known to us, CWDM(Coarse Wavelength Division Multiplexing) is a tech, multiplexing wavelengths transmitted in different optic fibers into one fiber to transmit via optical multiplexers. This tech is commonly seen in optical communications. However, What is CWDM? Maybe there still are many people confused about it. This article will have a introduction to us.

Originally, the term "coarse wavelength division multiplexing" was fairly generic, and meant a number of different things. In general, these things shared the fact that the choice of channel spacings and frequency stability was such that erbium doped fiber amplifiers (EDFAs) could not be utilized. Prior to the relatively recent ITU standardization of the term, one common meaning for CWDM meant that two (or possibly more) signals are multiplexed into a single fiber, where one signal was in the 1550 nm band, and the other in the 1310 nm band.

Seen from its literal meaning, CWDM is like that. Of course, the contents that CWDM gets involved in are far more than this. Then the next will introduce what CWDM is from the perspectives of CWDM characteristics, CWDM systems and CWDM applications.

In terms of CWDM characteristics, CWDM transmits few channels and makes use of wider spacing among channels for distances of up to 60 km. Its Transmission is operating via 18 channels with wavelengths between 1270 nm and 1610 nm(shown as the pic). It  is with relatively wide spacing of up to 20 nm, is able to tolerate relatively high temperature fluctuations and works between 1265 nm and 1625 nm.

Besides, it’s a cost-effective solution in metro and regional network, and can provide a capacity boost in the access network. It can meet demands in traffic growth without overbuilding the infrastructure. It is also perfectly alternative for carriers looking forward to increasing the capacity of their installed optical network without replacing existing equipment with higher bit rate transmission equipment, and without installing new fibers.

With respect to CWDM systems, they rely on optical signal regeneration at every node without the use of optical amplifiers. As all channels are regenerated at each node, the link power budget does not depend on the number of channels transported over each span. This simplifies the network design. Signal regeneration implies converting the signal from optical form to electronic form, and then reconverting the signal from electronic back to optical form using OEO (optical-electronic-optical) transponders. With signal regeneration, each wavelength requires its own individual transponder. Signal regeneration makes sense in networks with a limited number of spans and low channel count.

In respects of CWDM applications, it refers to these three aspects:

In LAN and SAN Connection: CWDM has abundant network topology, such as point-to-point, ring, etc. The ring network can provide self-healing protection function, the style of restoring including link breaking protection and node failure separation. CWDM rings and point-to-point links are well suited for interconnecting geographically dispersed LAN (Local Area Network) and SAN(Storage Area Network). Corporations can benefit from CWDM by integrating multiple Gigabit Ethernet, 10 Gigabit Ethernet and fibre Channel links over a single optical fiber for point-to-point applications or for ring applications.

Integrated in 10 Gigabit Ethernet: With the benefits of low implementation cost, relative simplicity of installation and maintenance, Ethernet has been used popularly in the metro/access system now. IEEE 802.3 Ethernet standards spawned a successive upward bandwidth migration from 10 to 100 Mbits to 1 Gbps. And as the bandwidth increases, 10 Gigabit Ethernet with higher data rate was put forward. Ethernet integrated with CWDM is one of the best implementing methods. 10 Gigabit Ethernet in the IEEE 802.3ae is a CWDM solution with four-channel, 1300nm. However, if CWDM were based on 10 channels of 1 Gbps, then 200 nm of the wavelength spectrum would be used.

In PON (Passive Optical Network): PON is a point-to-multipoint optical network that uses existing fiber. It is an economical way to deliver bandwidth to the last mile. Its costs come from passive devices in the form of couplers and splitters, rather than higher-cost active electronics. PON expands the number of endpoints and increases the capacity of the fiber. Although PON is limited in the amount of bandwidth, and CWDM can support. CWDM can increase the bandwidths cost-effectively. When they are combined together, each additional lambda becomes a virtual point-to-point connection from a central office to an end user. If one end user in the original PON deployment  needs his own fiber, he can get a virtual fiber by adding CWDM to the PON fiber. Once the traffic is switched to the assigned lambda, the bandwidth taken from the PON is now available for other end users. So the access system can maximize fiber efficiency.

It’s seen from above that CWDM is an economical and attractive wavelength multiplexing technology for city and access networks. For most users who want to increase their capacity of optical network and satisfy the demands on the growing demands. In addition, with CWDM applied in many networks, it will be more popular in the optical interconnection.

What Is Ethernet?

It’s known that Ethernet is created by Xerox, and jointly developed into the base LAN standard by Xerox, Intel and DEC. Although Ethernet is the most common communication protocol standard in present LAN, and it seems that there are still many people confused about the issue, what is Ethernet? And now, this article will introduce it for us.

The Definition of  Ethernet

Ethernet belongs to one of LANs with the widest range of applications, built in early of 70s; it’s an common LAN standard, whose transmission rate is 10Mbps. It consists of shared transmission media and cable, concentrator, Network bridge. With respect to its types, it’s made up of Standard Ethernet（10Mbit/s), Fast Ethernet（100Mbit/s）, 10G Ethernet（10Gbit/s）, adopting the CSMA/CD access control method and confirmed to IEEE802.3. In the Ethernet, all computers are connected into the same coaxial cable, and the CSMA/CD(Carrier Sense Multiple Access with Collision Detection) method, competition mechanism and bus topology architecture are adopted. In addition, the present Ethernet is available for the four kinds of transmission rates under the supports of fiber and twisted pair:

l  10 Mbps – 10Base-T Ethernet（802.3）

l  100 Mbps – Fast Ethernet（802.3u）

l  1000 Mbps – Gigabit Ethernet（802.3z)）

l  10 Gigabit Ethernet – IEEE 802.3ae

Evolution of Ethernet Technology

At the beginning, the Ethernet is only with 10Mbps handling capacity, uses CSMA/CD method. Such kind of Ethernet is called standard Ethernet, able to apply the coarse coaxial cables, thin coaxial cables, UTP (Unshielded Twisted Pair), STP(Shielded Twisted Pair) and fiber as the transmission media for connection. In the IEEE 802.3 standard, different physical layer standards are specially made for different transmission medias, in which the front number means transmission speed (unit: Mbps); the last number represents the length of one network cable(unit: 100m); the base means base band and the broad means broad band.

Then with the development of network, the traditional Ethernet is hard to keep pace with the gradually increasing needs in the flow rate of network data. Before October, 1993, for the LAN applications requiring over 10Mbps, only the Fiber Distributed Data Interface(FDDI) is alternative, but it’s the LAN with high price and based on 100Mpbs fiber cable. Therefore, in October, 1993, the Fast Ethernet came into sight. After that, the Gigabit Ethernet and 10G Ethernet also emerged respectively in the middle and later 1990s, and in 2002.

The Future of Ethernet

When it comes to the development of transmission rate, it’s believed that Ethernet is developed on the rising trend. In the past thirty years, Ethernet has been developed at the rate of  ten times all the time, from 10Mbps-100Mbps-1Gbps-10Gbps. Although the next step of Ethernet haven’t been confirmed whether it’s 40Gbps or 100Gbps, and the leading chip manufacturers in the field have produced the Ethernet chips, each one of which supports 20 ports of 10GE, and is testing the 100Gbps tech. Besides, its final goal is to provide the port-port Ethernet networks and Ethernet services.

Conclusion

Above all is about the Ethernet. What is Ethernet? As for this question, believing its answer is very obvious. By the way, there are various optical components for 10G Ethernet, such as 10G SFP+ AOC, 10G SFP+ AOC/DAC,  SFP+  optical transceiver module and so on. If you have any need for them, Welcome to contact Gigalight.