Gbic sfp difference

What are the differences between GBIC and SFP? When customers inquire about gigabit optical modules, what often comes to our minds is the SFP module. However, we tend to overlook another type of gigabit optical module – GBIC. Why has GBIC been gradually replaced by SFP? What is the relationship and difference between them? Let's take a look at their developmental journey.

What is GBIC?

GBIC (Giga Bitrate Interface Converter) refers to the Gigabit Interface Converter, which was quite popular in the 1990s. It is designed to be hot-swappable and adopts the SC interface. It is an interchangeable product that meets international standards. Gigabit switches designed with the GBIC interface are flexible in swapping and have a considerable market share due to this flexibility.

One end of it is a generic GBIC male connector, and the other end can be an electrical signal connector such as DB9, HSSDC, HSSDC2, or an optical signal connector like LC, SC. The generic GBIC plug is inserted into the GBIC female connector provided by the storage device, which requires the storage device to provide a GBIC female connector that meets industrial standards. The specific type of signal provided is determined by the type of GBIC. There are long-wavelength optical fibers that can run up to 5 kilometers, like the 1000BASE-LX GBIC WS-G5486. There are short-wavelength optical fibers, up to 500 meters, like the 1000BASE-SX WS-G5484. There's also a rare 1000BASE-ZX that can run tens of kilometers. SFP modules are half the size of GBIC modules, allowing for more than double the port configurations on the same panel.

GBIC modules are divided into two main categories: regular cascading GBIC modules and stacking-specific GBIC modules. Cascade GBIC modules are divided into four types:
1000Base-T GBIC module, suitable for Category 5e or Category 6 twisted pairs, with a maximum transmission distance of 100 meters.
1000Base-SX GBIC module, suitable for multi-mode fiber (MMF), with a maximum transmission distance of 500 meters.
1000Base-LX/LH GBIC module, suitable for single-mode fiber (SMF), with a maximum transmission distance of 10 kilometers.
1000Base-ZX GBIC, suitable for long-haul single-mode fiber, with a maximum transmission distance of 70 kilometers to 100 kilometers.

Stacking GBIC modules are used for cost-effective gigabit connections between switches. It should be noted that the GigaStack GBIC is specifically used for gigabit stacking between switches, and the connection between GigaStack GBICs uses a dedicated stacking cable.

With the popularity of small-form-factor optical modules like SFP, large space-consuming optical modules like GBIC have become obsolete and are currently only used in legacy network systems.

What is SFP?

SFP stands for Small Form-Factor Pluggable and can be simply understood as an upgraded version of GBIC. Its size is half that of GBIC, allowing for more than double the port configurations on the same panel. It's commonly seen nowadays, mostly with LC interfaces. The other functions of the SFP module are essentially the same as GBIC. Some switch manufacturers refer to the SFP module as miniaturized GBIC (MINI-GBIC), supporting SX, LX, TX, LH, and operating at 1000M.

The components of the SFP optical module include: a laser (consisting of a transmitter TOSA and a receiver ROSA), a circuit board IC, and external accessories. The external accessories include the casing, base, PCBA, pull ring, buckle, unlocking piece, and rubber plug. For easy identification, the pull ring's color typically indicates the module's parameter type. Unlabeled modules can be easily mixed up, so manufacturers usually differentiate them by the pull ring's color. For instance, black rings indicate multi-mode modules with a wavelength of 850nm; blue for a wavelength of 1310nm; yellow for 1550nm; purple for 1490nm, and so on.

The SFP transceiver is standardized by a multi-source agreement (MSA) among competing manufacturers. SFP is designed based on the GBIC interface, allowing for a higher port density (number of transceivers per inch on the motherboard) than GBIC. The related Small Form-Factor transceiver (SFF transceiver) is smaller in size than the SFP, but the SFF is soldered onto the motherboard as a pin through-hole device, rather than being plugged into a card slot.

SFPs are designed as pluggable transceivers adopting industry-standard cages and connectors and deliver high-speed performance in a compact package. The SFP was the first standardized form factor in this series, targeting applications with data rates up to 4G. To meet the demands for high-speed compact optical transceivers, the enhanced SFP+ was developed for applications reaching 10G or higher. SFP+ optical transceivers are interchangeable with SFP optical transceivers and can be used in the same SFP cages. For 10G applications, the SFP+ optical transceiver has a smaller footprint and consumes less power than XFP. Both SFP and SFP+ optical module motherboards have serial electrical interfaces.

SFP optical module rates include 155M/622M/1.25G/2.125G/4.25G/8G/10G, with 155M and 1.25G being the most commonly used in the market. The technology for 10G is gradually maturing, with demand growing steadily.
Categorized by wavelength, they include 850nm/1310nm/1550nm/1490nm/1530nm/1610nm. The 850nm wavelength is for SFP multi-mode, with a transmission distance of less than 2KM. Wavelengths of 1310/1550nm are for single-mode, with a transmission distance of more than 2KM. Generally, these three wavelengths are more affordable compared to the others.
 
 

1.Casing

The GBIC module's casing is quite large, being twice the size of the SFP module. GBIC uses an SC interface, while SFP primarily uses an LC interface.

2.Switch Application

Due to the interface differences between GBIC and SFP, the switches they apply to are also different. Switches that correspond to the GBIC module have GBIC slots, while naturally, switches corresponding to the SFP module have SFP slots.

3.Optical Fiber Connectors

Those who are not frequently exposed to optical fibers might mistakenly think that the fiber connectors of GBIC and SFP modules are the same, but they aren't. The SFP module connects to an LC fiber connector, while GBIC connects to an SC fiber connector.

4.Market Trend

In recent years, due to the smaller size of the SFP optical module, the GBIC optical module has gradually been replaced by the SFP optical module. Why is this? It's because the GBIC optical module's size is too large, taking up too much space on the switch, which results in the switch panel not being able to offer more interfaces. However, the smaller SFP optical module has solved this issue. For instance: There are switch panels with 48 SFP interfaces, but none with 48 GBIC interfaces.

5.Size and Form Factor:

GBIC: GBIC is larger in size.
SFP: SFP modules are much smaller than GBIC, hence the name "Small Form-factor Pluggable." Due to this smaller size, more SFP modules can fit on a single switch or router compared to GBIC.
 

6.Popularity and Usage:

GBIC: Earlier and older technology. It was widely used in older networking equipment.
SFP: SFP modules were introduced after GBIC and are seen as an evolution or replacement of GBIC. As a result, SFP has become more popular and widely adopted in modern networking equipment.
 

7.Hot-swappable:

Both GBIC and SFP are hot-swappable, which means they can be plugged in or removed without turning off the device.
 

8.Performance:

Both GBIC and SFP can support Gigabit Ethernet, but due to advancements in technology, SFP modules have been developed further to support higher rates (like SFP+ for 10 Gigabit Ethernet).
 

9.Compatibility:

SFP is sometimes referred to as Mini-GBIC due to its smaller size, but it's essential to understand that the two are not compatible. A GBIC slot in a switch cannot accept an SFP module and vice versa.
 

10.Connector Types:

Both GBIC and SFP modules utilize a range of connector types, but LC connectors are more common for SFPs, whereas GBICs might often use SC connectors.
 
In conclusion, while both GBIC and SFP modules serve similar functions, they differ primarily in size, design, and popularity. As of my last update in 2021, SFP modules are more widely used in modern networking equipment due to their compact size and broader range of applications.
Hopefully, through this article, you'll gain a better understanding of GBIC and SFP optical modules, and no longer be puzzled about which module to choose.